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The Baths of Diocletian in the year 2020 as seen from above and far away

Welcome to the Baths of Diocletian page, where I explore the largest bathing facility in the whole Roman Empire. Built in 306 AD, this luxurious and enormous Imperial Roman Baths served 10,000 people daily for 250 years. Much of this facility still exists, and it has been transformed into museums, gardens, and a stunning Basilica designed by the great Michelangelo himself. Entering this basilica is almost like entering the Baths of Diocletian when it was at its prime and covered in glistening marble and ornate decoration.

recreation of how the Baths of Diocletian looked from the western side of the bathing complex

The image above shows the large scale of the main baths building that was surrounded on all sides by gardens and walls containing many kinds of structures. Furthermore, the Baths of Diocletian was so huge that its outside swimming pool - the Natatio - was three times the size of an olympic pool and featured beautiful sculptures along the walls, as shown in the drawing below.

drawing of Romans bathing in the Baths of Diocletian Natatio pool in 320 AD
Romans enjoying Baths of Diocletian Natatio pool in 320 AD

I will look at the history, architecture, art, and many other aspects of this ancient bathing complex. And though some parts of the Baths of Diocletian have vanished, nevertheless, the vast ruins, thick walls, and spaces that exist today are still impressive and monumental.

To jump to a specific topic, please use guide below or keep scrolling and explore.

photo of what remains of the Baths of Diocletian today recreation of what Baths of Diocletian looked like in 306 AD
Baths of Diocletian in 306 AD compared to 2021 AD.


In 306 AD, with the completion of the Baths of Diocletian, Roman baths reached their peak not only in size but also in luxury. Even today, the current basilica inside the former ancient Frigidarium is still one of the most exhilarating interior spaces in the entire city of Rome.

This bathing facility was designed so that 3,000 bathers could use its facilities at the same time for a total of 10,000 every day. The location of the Baths is the Viminal Hill, the smallest of the seven hills of Rome.

This colossal building complex was a larger version of the already vast Baths of Caracalla, which opened 90 years earlier in 216 AD. When you stand in its centre, you can understand why, long after the Roman empire had fallen, people once thought that giants had built Rome.

Built of concrete and millions of bricks, the Baths of Diocletian was decorated lavishly with marble walls and floors, hundreds of columns, frescoes, mosaics, numerous statues, and large upper windows that filled the interior with sunlight.

Furthermore, the size of these baths, including the surrounding outside gardens, walls, and other structures, measured 13 hectares (32 acres). The actual main baths building itself was an incredible 4.5 hectares (11 acres) in size. One can only marvel at the labour, resources, expertise, artistry, and planning required to build such a massive complex in only eight years (298 - 306 AD).

Baths of Diocletian interior showing the 
central Main Hall and the frigidarium and tepidarium in the 4th century
Baths of Diocletian Main Hall in 4th century
From floor to ceiling was seven storeys in height
From a drawing by Edmond Jean-Baptiste Paulin, 1880, Modified

In ancient times, undoubtedly the Baths of Diocletian complex was an outstanding sight with its vast spaces, marble-covered walls, beautiful mosaics, statues, and frescoes. The image above aptly shows how massive this bathhouse was, and this is just a partial view of the Main Hall showing parts of the Frigidarium and Tepidarium areas.

Notice how the high, vaulted ceilings cover a considerable area of marble floorspace below. This high ceiling's vaults are supported by eight huge columns made of red granite from Egypt, and they are still there supporting the original ceiling today. These columns are 17 metres high (56 feet) and 1.6 metres wide (5 feet).

The incredible amount of detail and decoration you see displayed throughout the drawing above was typical of Roman design, which loved splendour and luxury. There is a pool on the left and right sides with an even larger pool in the distance. There are also large "tubs" at various locations on the floor. And, like many large Roman buildings, the brick superstructure was covered with marble on the inside and white stucco on the outside.

year 2008 photo of the interior of the Baths of 
Diocletian showing the main hall which has been converted into a church
Baths of Diocletian interior Main Hall in the 21st Century

In the image above, we see the same Main Hall of the Baths of Diocletian as it looks in the 21st century (2008). The view is of the same large, arched passageway on the right side of the fourth-century drawing above the photo. Amazingly, those reddish-granite columns and capitals (as well as the ceiling) in the drawing have miraculously survived a 1,700-year journey through sackings, wars, pillaging, earthquakes, and neglect.

If you think that the photo above looks like the inside of a church, you are correct. In the 16th century, this church was designed by the great artist and architect Michelangelo. He built this church (basilica) while using as many of the original materials as possible, within the ancient Frigidarium and Tepidarium, of the Baths of Diocletian.

During the work, the floor was raised 2 metres (2 yards) because the outside ground level had risen over the centuries. Moreover, the entrance to this church - which is actually a basilica - is through what remains of the former circular Caldarium, shown in the image below. When people pass through the doors of this basilica, they are entering the former Tepidarium section of the baths, which has a magnificent dome with a hole (oculus) in its centre. This dome is a smaller version of the great dome found in the Pantheon.

photo showing the entrance area to the Basilia of Santa Maria degli Angeli inside the former Baths of Diocletian in the year 2010
Entrance to St. Mary of the Angels & Martyrs Basilica
The rounded entrance is part of the ancient Caldarium
Image courtesy of Justin Ennis - CC BY 2.0

As you can see, most of the Caldarium entrance is now gone. And though the entrance may look very worn and damaged, the interior of the church is actually stunning and quite beautiful. The bluish doorway on the left is part of the western section of the Baths used as a granary, an orphanage, and a poorhouse for women.

The basilica entrance faces south towards a large plaza called the Piazza della Repubblica built in 1898. This entrance changed drastically in appearance from 1749 to 1911 AD, which I will discuss in detail later.


drawing showing west side of Baths of Diocletian in 320 AD
West Side of Baths of Diocletian in early 4th Century AD

Built during the years 298 to 306 AD, an interesting fact about these baths is that they were not built by Roman Emperor Diocletian (244 - 311 AD) at all. In fact, by the time the baths finally opened, he was no longer an Emperor.

Diocletian may never have seen these baths because he did not live in Rome; instead, he lived his entire life in the Eastern Roman Empire, where he was born in present-day Croatia. However, because he visited Rome in the year 303 AD for the 20th anniversary of his rule, he may have looked at the bathhouse while it was still being constructed.

photo of a Roman gold coin featuring the likeness of 
Emperor Diocletian
   photo of a Roman gold coin featuring the likeness of Emperor Maximian

The person who commissioned and built the Baths of Diocletian was Emperor Maximian, who co-ruled the Roman Empire with Diocletian. They both ruled the Roman Empire from 286 to 305 AD, although Diocletian was an Emperor starting in 284 AD.

The Western half of the Roman Empire, where Rome was located, was ruled by Maximian and the Eastern half was ruled by Diocletian. Despite this division, the empire was not really split. It just got so big that it was too much for one Emperor to handle. This arrangement was similar to when the Roman Empire was co-ruled by Octavian (Augustus) in the West and Marc Antony in the East for ten years after the death of Julius Caesar in 44 BC/BCE.

An interesting fact is that, before the baths were completed, both Maximian and Diocletian abdicated in the year 305 AD, the only Roman Emperors to willingly do so. However, while Diocletian never became an Emperor again, Maximian came out of retirement quickly and tried to take power a few times before being forced to commit suicide by Emperor Constantine the Great.

It is said that thousands of enslaved Christians - possibly 40,000 or more - did the hard work of building the baths. It is possible Christians were used as slaves because Emperor Diocletian was hostile towards Christians and instigated policies that persecuted them. And that is why there is a church within the ruins dedicated to Christian martyrs who died while building the baths.


The alternating diagrams below show the outlines of the Baths of Diocletian and the Baths of Caracalla, so you can compare them. You will see that the main building of the Baths of Diocletian was larger. However, you will also notice many similarities such as:

•   Both had the same basic arrangement of bathing pools (Frigidarium, Tepidarium, Caldarium, Natatio), exercise courts (Palestrae) and changing rooms (Apodyteriums).

•   They were both surrounded by gardens, fountains, pools, and a wall containing towers and exedrae (plural of exedra).

Another shared characteristic is that both these baths were built mainly of bricks and concrete covered with a marble veneer on the inside and white stucco on the outside.

In the diagrams below, please note that, although the Baths of Diocletian main building is 20% larger, the Baths of Caracalla complex (building and surrounding gardens, walls, etc.) occupied a more extensive area - 25 hectares (62 acres) versus the Baths of Diocletian's smaller 13 hectares (32 acres).

map outline of Baths of Caracalla showing arrangement of bathing pools map outline of Baths of Diocletian showing arrangement of bathing pools
Baths of Diocletian map compared to Baths of Caracalla

Notice how the Baths of Caracalla has large and circular exedras on the lower left and right sides of its outside wall. In comparison, the Baths of Diocletian, in addition to its huge bottom theatre exedra, also has numerous circular and rectangular exedras all along the other three surrounding walls.

The semi-circular exedras are said to have a "hemicycle" shape, meaning semi-circular. The arrangement of the water pools is precisely the same. In addition, both baths have two Palestrae (exercise area) areas, one on either side of the Frigidarium water pool.


The moving panorama below shows the Eastern facade and then the Western facade of the Baths of Diocletian in the fourth century when the whole structure was standing. These baths were enormous and covered a vast expanse of ground estimated at 140,000 square metres (1,500,000 sq. feet). The highest point of these buildings, the Main Hall in the centre of each facade, was over 30 metres (100 feet) high. As you watch the facades of these baths scroll by, keep in mind that a person standing next to these buildings would appear tiny.

video showing a moving panorama of the east and west side of the Baths of Diocletian as it appeared in the year 320 AD / CE
Video panorama showing East and West side of the Baths of Diocletian in 320 AD
Video created using

As shown in the video above and image below, the Baths of Diocletian complex was very extensive, a characteristic of a Thermae baths, also known as an Imperial Baths. Much land was required for all the areas associated with the main baths building, such as the gardens, courtyards, and other smaller buildings all enclosed with walls and towers. I have labelled some of the various sections in the image below. The Romans called a gymnasium or exercise courtyard a Palaestra.

316 AD view of the Baths of Diocletian from above with the various sections labelled
Baths of Diocletian main areas in 4th century

Because the images above identify only the major sections of the Baths of Diocletian, below is a complete breakdown of all the different areas and structures associated with this vast baths complex. Four Main Pools refer to the Frigidarium, Tepidarium, Caldarium, and Natatio main pools:

 •   Four Main Pools;
 •   Gymnasiums;
 •   Saunas;
 •   Changing Rooms.
 •   Long Great Halls; 
 •   Entrances
 •   Oiling Rooms
  •   Large theatre;
  •   Libraries;
  •   Lecture halls;
  •   Gardens & Walls;
  •   Swimming Pools;
  •   Courtyards;
  •   Vendors.

The Baths of Diocletian grounds housed a theatre inside a huge, semi-circular exedra that extended beyond the outside walls. This very prominent exedra, labelled "theatre" in the image above, has been destroyed over time; however, the ancient outline was preserved by the current buildings facing the Piazza della Repubblica, seen in the image below.

At the centre of this plaza is a large fountain, the Fontana delle Naiadi. The buildings seen today were designed by Italian Architect Gaetano Koch in the late 1800s. In his design, he made sure to follow the outline of the former ancient exedra when placing the buildings.

photo of 'Piazza della Repubblica' in 
Piazza Della Republicca in 2019
Buildings arranged along round outline of ancient Exedra

You can see how huge this exedra was, and it is fascinating how the current plaza still preserves the outline of the ancient exedra. How did this happen? Perhaps, over the centuries, much of the exedra structure remained; and, over time, buildings were built along the periphery of the ancient structure.

Or, perhaps Mr. Koch demolished those parts of the exedra that still remained in addition to buildings covering or adjacent to the ruins. As explained further down, parts of this exedra were still standing in the 1600s. This massive exedra/theatre complex is unique to the Baths of Diocletian because the Baths of Caracalla has a large water reservoir made up of many cisterns instead of a theatre in its layout.

photo of the Fountain of Naiads in the Piazza della Republicca in front of the Baths of Diocletian in Rome
Fountain of Naiads in the Piazza Della Republicca
Licensed from

In 1888, the current fountain, pictured above, was designed and built by architect Alessandro Guerrieri, and this replaced another fountain there dating from 1870. The current fountain kept evolving over a few decades until it was finally completed in 1912.

Stone statues of lions were replaced by four bronze statues of Roman water nymphs called "Naiads" created by Mario Rutelli. He also created the central statue of the Roman sea god Glaucus Pontius. This large and beautiful fountain lies in the heart of the former exedra of the Baths of Diocletian.

engraving from the year 1551AD showing the still-standing exedra theatre of the Baths of Diocletian in the lower 
      part of the image with the ruins of the still-standing Caldarium in the upper part of the image.  To the far left is a rotunda
      tower which today is the church of San Bernardo alle Terme.
Baths of Diocletian Exedra and Caldarium in 1551 AD
G.B. de'Cavalieri and G.A. Dosio - 1551 AD

The exedra still existed in the 1550s, as shown in an engraving above. In the foreground of the image, you can see the curved wall of the exedra still standing as it faces the Baths of Diocletian's western side. At the far left is a round tower which is an ancient, domed rotunda building which today is the church of San Bernardo all Terme.

The baths building with two second-floor "windows" in the upper centre-right of the image is the Caldarium which was demolished in 1587 by Pope Sixtus V. Unfortunately, all that remains of the Caldarium today is a curved, concave wall with an entrance leading into the basilica inside the baths.


Below is a collection of images showing various sides of the Baths of Diocletian in the 21st century. These photos show how large this bathing complex still is despite much of it now now being gone. I show photos taken from different sides of the baths complex, including an overhead view. The building lies on a southeast to northwest trajectory.

View of main 
Baths of Diocletian building in year 2020
Looking North at the main Baths building
Image Courtesy of Luis Fernando Murillo

In the photo above, we are looking at the eastern side of the Basilica, which borders the former gymnasium area. In the next photo, the view will be in front of that palm tree and looking right.

Northeast view of main 
Baths of Diocletian building
Looking Northward
One of the baths two gymnasiums (Palaestra) was located here
Image Courtesy of Carlos Espejos

This now vacant space was where the eastern Palaestra, a long and spacious gymnasium courtyard, was located. This photo conveys the extensive size of this ancient gymnasium. Below the largest window on the left is where the main entrance to the basilica was located, as designed by Michelangelo.

One hundred eighty years later, this entrance was walled off by Clemente Orlandi around 1746. To see this entrance area in the year 1551, click this link, and you will see that that whole large window, right down to the ground, used to be open before the window and wall below were added.

On the right side, you can see the distant Hall IX, which is used currently to display ancient sculptures and architectural remnants. This hall is one of several on the eastern side of the baths.

Southwest view of 
Baths of Diocletian building showing the Natatio wall with niches
Looking Southwest at Natatio wall
Part of the great facade, once made of marble and mosaics, facing the outside Natatio pool

This is a view of one section of the "rear" wall of the baths, opposite the entrance side. In the ancient past, this wall formed a wide facade made of marble panels, columns, sculptures, and coloured mosaics that created a dynamic reflection on the surface below of the enormous Natatio outdoor swimming pool. The size of this pool was three times that of today's Olympic-sized pools.

Despite the pillaging of practically all the fine decorative materials, the facade's height, scale and intricate architecture is still impressive. And here and there, one can still see some chunks of white marble the pillagers did not manage to remove. The shape and position of these surviving pieces of marble indicate where tympanums, columns, and entablature were located. One can only imagine how grand and awe-inspiring it must have looked so long ago.

Looking Northwest at Baths of Diocletian from Via Cirnaia street that goes through the ruins and showing 
the Octagonal Hall and an exedra
Looking Northwest from Via Cirnaia street that now goes through the ruins
Cars are parked in west side gyymasium (Palaestra) area
Ancient domed building on left is the Octagonal Hall
Image Courtesy: Darren & Brad - CC BY-NC 2.0

When a large train station was built nearby in 1867, it changed the neighbourhood considerably. For example, Via Cernaia street (shown above) was built through the west side ruins in 1878. In the upper left, the Octagonal Hall rotunda with its intact dome is seen. Connected to the rotunda are the ruins of a wall that marked the western edge of the main baths building. In the foreground is the location of the western Paleastra gymnasium which is now filled with a street and parked cars.

photo showing how the entrance to the basilica of Santa Maria Degli Angeli is the caldarium of the Baths 
of Diocletian
Entrance to the basilica is a wall of the Caldarium
Image courtesy of David Kohlmeyer - CC BY-NC 2.0

To access the basilica of St. Mary of the Angels and Martyrs, one goes through the main entrance on the left. When standing directly in front of this entrance, you will notice that the partial walls on either side are curved - this is because these walls are the remains of the large and circular Caldarium area of the building.

After proceeding through the main entrance, you immediately enter a large room with a dome. This room is the former heated Tepidarium area that provided warm baths for the patrons. The large structure on the far right of the photo above is the basilica within the former Frigidarium.

photo of the entire Baths of Diocletian complex seen from the air and looking south towards the Piazza della 
Baths of Diocletian complex seen from the air, looking south
Image courtesy of Google Earth

In this final photo of the exterior of the baths, I show the whole complex from above, looking south. On the left is the eastern side containing various halls that display ancient art. On the right is the western side, showing Via Cernaia going through the ruins and separating the western edge from the main baths.

In the middle is the large basilica of Santa Maria degli Angeli e dei Martiri (St. Mary of the Angels & Martyrs), with the Small Cloister and part of the Large Cloister located below the basilica. At the top, you can make out the vast semi-circle of the Piazza della Repubblica which occupies the site of the former huge theatre exedra of the Baths of Diocletian.

The domed Octagonal Hall is in the top-right corner. Furthermore, the vast wall facade that faced the now-vanished Natatio can be seen stretching all along the breadth of the basilica.


photo of Baths of Diocletian interior frigidarium 
in the year 2019 AD which was transformed into a church in the 1560s AD
In the 21st century, the Frigidarium is now a church
Interior of basilica looking north

The inside spaces of the Baths of Diocletian have certainly changed over the 1,700 years since it opened in 306 AD. A visitor to these baths today will undoubtedly notice that the interior parts of the Baths of Diocletian vary dramatically, and many sections no longer exist.

While some areas of the baths resemble how they looked in the fourth century due to renovations, other areas have been reduced to bare brick and concrete due to fifteen centuries of pillaging and neglect. Fortunately, the basilica's beautiful vaulted ceiling and eight supporting columns are the original structures that astonishingly survived 1,700 years.

This ceiling, of course, is the Main Hall of the former Frigidarium area, shown in the photo above. In addition, the domed ceilings of the former Tepidarium and Octagonal Hall also have survived.

Despite the unfortunate reality that many parts of the Baths of Diocletian have been lost, the remaining sections have been converted into two churches and various museums where ancient art and other antiquities are displayed. These areas of the Baths of Diocletian in the 21st century are explored further on this page.



painting of the great artist Michelangelo
Michelangelo Buonarroti 1475-1564
Worked on the basilica 1561-1564


‌In the very heart of the largest Roman baths in Rome, one finds a Catholic Basilica built inside the former Frigidarium and Tepidarium sections. The odds of an ancient Roman building surviving the ravages of time significantly increased if it was converted into a church.

However, unlike the Pantheon, which was converted into a Christian church early in 609 AD, it took an additional 950 years for the Baths of Diocletian. That was almost ten centuries during which the baths were abandoned, neglected, and pillaged for materials.

Fortunately, due to its vast size, solid construction, and some luck, the central area of the ancient baths retained its vital column and roof infrastructure - this made the process of conversion much more feasible and successful.

Two critical periods in European history were the Roman Empire and the Renaissance. These two eras became joined in the transformation of part of the Baths of Diocletian into a basilica in the 1560s.

Another important consideration regarding the transformation is how it helped to preserve and bolster the baths crumbling infrastructure. By the 16th century, the Baths of Diocletian's structure was considered so hazardous that the public was barred from accessing the site. The authorities worried that parts of the structure might fall on people's heads.

The history behind this remarkable conversion from Roman ruin to Renaissance basilica is quite fascinating, and it involves one of the Renaissance's greatest artists, as explained below.

photo of interior of basilica of Santa Maria 
degli Angeli e Martiri, a wide view, inside the Baths of Diocletian in the year 2008 AD
Santa Maria Degli Angeli e dei Martiri interior in 2008
Photo courtesy of Leonardo (sgotto) - CC BY NC-ND 2.0


In 1561 AD, Pope Pius IV commissioned Michelangelo Buonarotti to transform the Frigidarium and Tepidarium sections of the Baths of Diocletian into the church of Santa Maria degli Angeli e dei Martiri (St. Mary of the Angels & Martyrs). The Church believes that many Christians died while being forced to build the baths during the years 298 to 306 AD.

Twelve hundred years later, a young priest from Sicily by the name of Antonio Lo Duca had a vision in 1541 AD that ultimately led to the creation of a church inside the ancient baths. In his vision, he saw a bright light over the Baths of Diocletian, and he beheld seven Angels that had given relief and assistance to Christian martyrs forced to build these baths.

Antonio believed his vision meant God was telling him a church must be built in the ruins of the Baths of Diocletian to honour the Christian martyrs and the seven angels - and thus the reason for the words "Angeli" (angels) and "Martiri" (martyrs) in the church name.

artistic recreation of Baths of Diocletian interior showing one of the great halls filled with bathers
From Roman Baths to Catholic Basilica
Frigidarium in 306 AD

However, it took many years of pleading his case to various church officials before Pius IV, Pope from 1559-1565, finally agreed to finance renovating the baths into a church. The considerable task of the renovation was given to Michelangelo, who began working on the project in 1561.

In his usual brilliant fashion, Michelangelo, at the age of 86, used the original parts of the baths as much as possible as he adapted the remaining structures of the baths' central area into a church basilica. Unfortunately, in 1564, he passed away before finishing the work of transforming the baths into a basilica.

Michelangelo's project thus had to be completed by one of his students by the name of Jacopo Lo Duca. This man, coincidentally, was the nephew of Antonio Lo Duca, who had the vision of angels.

Almost 500 years later, and after more renovations, this church still looks impressive inside. Entering it is almost like visiting this part of the baths in the fourth century when it was filled with tall columns, elegantly carved marble decorations, walls covered with marble panels, and gleaming floors made of inlaid marble and granite.

The success of Michelangelo's renovation is undeniable. Just like the ancient Roman architects before him, he created a sensation of huge, beautiful spaces that amaze and delight the eye.

Baths of Diocletian interior as it looks today inside the church of 'Santa Maria degli Angeli e dei Martiri' showing 
how the columns, walls and floors are almost the same as during the fourth century AD
Baths of Diocletian showing view of north and northeast areas
Courtesy of Lawrence OP - CC BY-NC-ND 2.0

An amazing fact about the photo above is that many of those columns and the marble capitals are the ancient originals that survived over 1,700 years. The red granite columns were quarried in Egypt and shipped to Rome, which was a huge undertaking as each 12-metre long column (40 feet) weighed 100 tonnes.

So though this church is not really an exact reproduction of what the ancient baths looked like, you can still get a good approximation of the splendour of ancient Roman architecture, akin to the experience of seeing the interior of the Pantheon.

Upon seeing the interior of Santa Maria degli Angeli e dei Martiri for the first time, I was impressed by the soaring ceilings, huge columns, and intricate marble decoration throughout the vast space. And when you consider that this whole church occupies only a small part of the whole baths - one begins to understand how vast and impressive these ancient baths must have been in their prime.

The carved marble detailing shown in the photo below is outstanding. The amount of work and skill needed to achieve this level of elegant architecture is truly impressive. So often, when we see Roman ruins, these kinds of details have either been pillaged or worn down to just a shadow of their former glory. This same level of artistry is also evident in the Pantheon, which again demonstrates how beautiful Roman architecture was and how much we have lost.

Closeup photo of a marble capital inside the Baths of Diocletian showing the exquisite details
Photo of the exquisite marble carving above the columns
Courtesy of Lawrence OP - CC BY-NC-ND 2.0


panoramic view of ceilings of church of
Santa Maria Degli Angeli e dei Martiri in Baths of Diocletian
The vaulted ceilings of Santa Maria Degli Angeli e dei Martiri church in the Baths of Diocletian

The eight red granite columns that support the vaulted ceiling are the original ancient columns that came from Egypt. The ceiling and the capitals atop those eight columns are also ancient and have survived into the 21st century. In my 2019 photo above, you can see this vaulted ceiling which has had a combination of plaster and paint applied to it during 1560s renovations of the baths.

Also in this photo, you can see where eight ceiling vaults come down and make contact with the eight original columns. And those columns were actually much higher in the past because they stood on top of a 2-metre high (6 feet) rectangular plinth which disappeared from view when the floor was raised.

If you have seen the ceilings of other very old and great churches in Italy, you will notice quite a difference. The ceiling we see here is white, unadorned, and simple. This ceiling is unlike other church ceilings that are covered in frescoes and decoration. I am glad they left the ceiling of Santa Maria degli Angeli pure and white.

You may notice there are several dark spots, which may be where lighting, such as chandeliers, were suspended - but I am guessing at what they might be. I do remember reading an article describing those ceiling spots as the "original bronze rosettes from which lighting was hung." If those spots really are "bronze rosettes," then when were they created? During Roman times or the Renaissance? Unfortunately, I could not find any further information. Next time I am in Rome, I will enter the basilica and use binoculars to get a good, close look to see what they really are, other than just dark spots.

photo of light spectrum highlight on marble floor of Santa Maria 
degli Angeli basilica
Play of light coming from the ceiling windows on the marble floor of Santa Maria degli Angeli
Image courtesy of Mararie - CC SA-by-2.0

Another wonderful effect of this ceiling, as shown above, is how it works with the surrounding large windows to create a pleasant effect of light on the inlaid marble floors and walls when the Sun is shining. Somehow, the pure white light is refracted by the windows to produce a rainblow-like effect of many colours - this compliments both the colours of the floor marbles and the large paintings on the walls.

I noticed that the effect stopped when clouds covered the Sun. At first, I assumed that, like other old churches, the basilica had stained glass windows casting coloured light on the floor - but that is not so.

The only stained glass in the whole basilica was located in the main entrance area (facing the Piazza della Republicca). In ancient times, this entrance area to the basilica was the Tepidarium, which is still covered with a dome with a large hole in its centre, just like the Pantheon. It is a beautiful dome with a rosette in each of the 168 coffered panels.

Tepidarium dome of the Baths of Diocletian in the year 
2010 where it is now forms part of the entryway to the basilica of Santa Maria Degli Angeli e dei Martiri
Entryway dome of Basilica of Santa Maria Degli Angeli (2010) which was the former Tepidarium of the Baths of Diocletian
Image courtesy of Shando - CC SA-by-2.0

In ancient times, this dome's opening, called an oculus, was open to the sky, and rain fell into a pool below. However, now it is covered. In the year 2001, the artist Narcissus Quagliata made a 5-metres wide (16.5 feet) stained-glass cover for the hole.

The top of this dome sits 23 metres (75 feet) above the floor. Actually, there was another glass cover, but it was of a yellowish hue that did not compliment the basilica's interior. Also, it allowed rain to enter, which caused water damage - and so it was replaced by this pleasing and modern stained-glass creation. To see a closeup of the stained-glass cover, click this link.

Diagram showing how the roof and ceiling of the Baths of Diocletian Frigidarium is constructed.  This structure is now known as 
the Basilica of Santa Maria Degli Angeli e dei Martiri in the 21st century
Roof and ceiling construction of the Basilica with the Frigidarium of the Baths of Diocletian


The ancient Roman architects made extensive use of arches to create Groin Vaults that could form ceilings over large areas. But if an arch is supporting substantial weight, it could collapse if both ends of the arch are not strongly supported.

The trick was to use thick walls and reinforcements, called Buttresses, at either end of the arch to make it stable and strong. The ceiling of the Main Hall of the Diocletian Baths is made entirely of Groin Vaults which I show in the photos and diagrams below. Each of the four arches within the three inner "X" formations is a "groin" where all four groins join together and reinforce each other (blue circle).

Roof of frigidarium of Baths of Diocletian showing where eight original supporting columns and buttresses are located in the 
year 2020 AD
Frigidarium "Main Hall" Roof showing Groin Vault structure and Buttresses

diagram showing groin vault ceiling 
of Baths of Diocletian main hall and also showing other arched/vaulted structures within the baths
Diagram showing groin vault roof structures in the Diocletian Baths' Main Hall and surrounding sections
Image courtesy of Researchgate

In the diagram below, I show how an arch can be reinforced and stabilized by buttresses. You can see how the bottom left and right sides of the arch are under considerable pressure due to gravity.

Moreover, the force is pulling not only down but also to the sides, which could cause a collapse. The buttress at either end of the arch helps to counter any tendency of an arch to collapse by pressing up against either end of the arch.

A buttress is especially important when a column supports two or more arches, as is the case in the Baths of Diocletian frigidarium Main Hall. Each of the eight original columns supports at least three and sometimes four arches.

Baths of Diocletian interior as it looks today inside the church of 'Santa Maria degli Angeli e dei Martiri' showing 
how the columns, walls and floors are almost the same as during the fourth century AD
Buttress reinforcing arch at both ends

This principle was used extensively throughout the Middle Ages in the construction of Gothic cathedrals, which used a similar type of arch/vault system called Rib Vaults as opposed to the ancient Roman Groin Vault. Long after the fall of the Western Roman Empire, many Roman ruins remained to show later generations how to build huge structures, as explained in this great article about gothic and romanesque architecture.


After the destruction of many aqueducts supplying water to Rome in 537 AD, the Baths of Diocletian were no longer used. And then, for over 1,000 years, the baths remained abandoned until the 1560s, when Michelangelo began converting the baths Frigidarium into a church. However, by this time, much of ancient Rome was now covered by several metres of sediment and debris.

Because the ground level outside the Baths of Diocletian was much higher than the inside floor level, Michelangelo decided to raise the floor so that it matched the outside ground level.

Therefore, the floor inside the baths was raised by 2 metres (6 feet), which brought the floor surface to just below the bottom of the eight ancient columns still supporting the Main Hall ceiling. In the photos below, the 306 AD lower floor level changes to the current higher floor level raised in the 1560s during Michelangelo's modifications.

image showing what the actual ancient floor level of the churhc of Santa Maria degli Angeli e dei Martiri was in ancient times before 
Micehelangelo's renovations in the 16th century
Ancient Floor Level
photo of the floor and colums of the church of Santa Maria degli Angeli e dei Martiri in 2019 AD showing the floor ground 
level today
Current floor level
Photo by That_Bee - CC BY-NC 2.0 - Modified

The massive red granite columns stood on 2-metre high (6.75 ft) rectangular plinths that mostly have been buried during the floor raising process in the 1560s. In the images above, I have lowered the floor back to its original level, thus fully exposing the ancient plinths. The image shows how much taller the columns were in the ancient past.

Today, just a small part of the plinths can be seen below the bottom of each column's torus. The ancient frigidarium hall likely was more impressive to the Romans because the ceiling was higher, thus creating a larger space. The hall we see today, though still impressive, is nevertheless truncated.


wide view of the Small Cloister 
in the Baths of Diocletian in Rome in 2015
View of the Small Cloister of the Baths of Diocletian
By special permission ©
Linden Gledhill

Before exploring the cloisters of the Baths of Diocletian, I will explain the background history and characteristics of both the Small Cloister and the Large Cloister. On the grounds of the former Baths of Diocletian, you will find two four-sided courtyards, one much larger than the other.

These courtyards are called "cloisters," and the larger one is the biggest in Italy. Because these cloisters were built in the 16th century, they did not exist during Roman times. In fact, both cloisters were built on top of the ruins of the Baths of Diocletian. Furthermore, as regards the Large Cloister, parts of the baths were actually demolished to make space for it. The image below shows the small and large cloisters from the air above the Baths of Diocletian. You can see how the Small Cloister is located above the upper left corner of the Large Cloister, and it is much smaller in size.

photo of the Baths of Diocletian from 
high above that highlights the location of the Small and Large Cloisters
The location of the Small and Large Cloisters
Image produced using Google Earth

The reason why they are called "cloisters" is that they are a form of colonnaded (columned) courtyard associated with monasteries, convents, and churches. For over three centuries, from the 1560s until 1881, a monastery existed within the baths, and it is now used to display Roman statues as part of the "National Roman Museum."

Painting of several Carthusian monks seated
at a table and welcoming a guest in 1655 by Francisco de Zarbaran
Carathusian monks in 1655 welcoming a guest
By Francisco de Zurbarán - Museo de Bellas Artes de Sevilla

When Pope Pius IV commissioned Michelangelo to convert the central part of the Baths of Diocletian into a church, he also decided to make Carthusian monks the caretakers of the baths. However, to fulfill their duty, these monks required a Charterhouse, which was built and existed in the Baths of Diocletian until 1884. The cloisters were built to house and serve the needs of the monks, who typically wore white robes, as shown in the 17th-century painting above.

The monks who follow this order still exist today. However, their order is still secluded, and they live almost like hermits, living a life of work, silence, and contemplation. They live in cells along the four sides of a courtyard known as a Cloister, where they spend most of their lives in seclusion from one another. In the Baths of Diocletian, their cells were located along the four colonnaded hallways of the Larger Cloister.

photo of the well in the Small Cloister of the 
Baths of Diocletian
The well in the centre of the Small Cloister
Licensed from

Very close to the basilica, on the northeast side, a small courtyard of light-coloured stone brick floor can be found - this is the Small Cloister, which is very reminiscent of cloisters in Naples, Florence and other parts of Italy. This cloister is very simple, with small columns, a stone courtyard floor and a small well in its centre.

As shown in the photo above, despite this cloister's simplicity, it is nevertheless quite beautiful. The entire Small Cloister was built above one-third of the ancient Natatio swimming pool area, which is now mostly filled in. However, a small part of the ancient Natatio still exists and can be seen by the public - the photo below shows what remains.

Photo of what remains of the huge Natatio
 swimming pool of the ancient Baths of Diocletian in the year 2020
What remains of Baths of Diocletian's Natatio Pool in 2020 AD
By special permission © Anton Skrobotov

In the photo above, the far left wall is the Small Cloister. The brick walls on the right are part of the basilica - in Roman times, they were covered in marble, and the niches held statues. You can still see some traces of the original marble in the brick where columns and colourful mosaics were affixed. To the left, the viewer is looking southeast towards Hall VIII - the door of Hall IX also can be seen.

Photo of a high-relief Roman sculpture
from the Ludovisi collection in the Roman National Museum at the Palazzo Altemps in 2020
Barbarians - Ludovisi collection, Palazzo Altemps
This high-relief was displayed in the Small Cloister until 1997
Image courtesy: Carolyn Whiston - CC BY-NC-ND 2.0

Within the columned corridors of the Small Cloister, various statues are on display. Until recently, this cloister held famous marble statues and reliefs from the Boncompagni-Ludovisi Collection - an example of a Ludovisi high-relief is shown above. Because of this association with these statues, this cloister is also known as the Ludovisi Cloister.

In 1997, the Boncompagni-Ludovisi collection of statues was moved to another part of the National Roman Museum called the Palazzo Altemps.

Besides statues, the cloister also displays historical documents of the Roman Catholic church. Below are photos of Roman statues currently on display within the colonnaded courtyard hallways of the Small Cloister.

Photo of the Small Cloister of the Baths of Diocletian showing a colonnade interior with statues
Small Cloister Colonnade with statues displayed
Licensed from

Photo of the Small Cloister of the Baths of Diocletian showing a colonnade interior with an ancient  standing 
white marble statue Roman Marble Statue
Licensed from
Photo of the Small Cloister of the Baths of Diocletian showing a colonnade interior with an ancient  statue 
head of a man with a beard Bust of Roman God Zeus
Licensed from


The Large Cloister, also known as Michelangelo's Cloister, is the largest in Italy. Each of the four sides of this large space measures 100 metres (330 feet) and contains over 100 solid travertine columns supporting arches. Within these colonnades are around 400 statues, decorative architectural objects, and sarcophagi. The interior of this large cloister is a large green space.

Whereas the Small Cloister was built primarily on top of the former Natatio outside pool, the Large Cloister was built over the northern ruins of the Baths of Diocletian and it extends past the northern wall limit of the baths.

wide view of the Large Cloister, also known as 'Michelangelos Cloister'  
in the Baths of Diocletian in Rome in 2019
View of Michelangelo's Cloister of the Baths of Diocletian 2019

You can see why this is considered the largest cloister in Italy. It is very wide, and each of the four sides contains 25 columns supporting arches within the two-storey structure. The broad expanse of grass, trees and plants provides a soothing retreat from the heat and congestion of Rome in summer. It is an oasis of quiet and contemplation in the heart of the bustling city of Rome.

photo showing one of 
the four colonnaded sides of the Large Cloister of the Baths of Diocletian in 2014 showing some sculptures on display within 
the colonnade hallway
One of the four colonnades displaying sculptures

On the left, you can see many ancient Roman sculptures along one of the colonnaded hallways of the Large Cloister. The right side shows the top of the Baths of Diocletian's frigidarium (now a church) looming above the cloister. The chimney-like structure is part of the Natatio wall facade.

Photo of fountain and cypress trees 
in the centre of the large cloister (Michelangelo's Cloister) of the Baths of Diocletian taken in the year 2019
Fountain and cypress trees at the centre of Michelangelo's Cloister
Image courtesy: Jamie Heath 2019 -
CC BY-SA 2.0

The heart of the Large Cloister has a lovely fountain surrounded by trees, hedges, and large statues that combine to create a wonderful garden and refuge. I am sure the Carthusian monks found this retreat very relaxing and comforting. Tradition says some of the large Cypress trees were planted by Michelangelo in the 1560s while working on the Basilica. If he actually did plant theses trees, they are now over 450 years old.

The series of four photos below show some of the fantastical carved-stone animal heads found in the Forum of Trajan. They are at least 1,900 years old, and they are so different from typical Roman sculptures.

I am sure these wonderful animal statues really delighted Roman children so long ago and probably still do today. Many thanks to both Jamie Heath and Brad Hostetler for all the great photos in this section and for making their work available for educational use.

photo showing four ancient animal heads
 inside the Large Cloister 
of the Baths of Diocletian in 2018.  These carved stone animal heads originally came from the Forum of Trajan
Stone animal heads from Trajan's Forum in the Large Cloister
Images courtesy: Brad Hostetler 2018- CC BY-SA 2.0

The image below shows how the Large Cloister extends considerably beyond the ancient walled perimeter surrounding the grounds of the Baths of Diocletian. Left of centre, you can see the outline of an ancient exedra and wall, which show where the ancient boundary was - I have indicated the boundary with yellow hyphens.

When building the Large Cloister for the Carthusian monks, the ancient ruins that were in the way were demolished, unfortunately. You can see how this cloister extends past the northern wall boundary of the former baths.

map diagram showing how the Large Cloister of the Baths of Diocletian extends far beyond the ancient boundaries of the 
baths complex
The Large Cloister extends beyond the baths' original boundaries
Original image courtesy of Google Earth

If you visit the Baths of Diocletian, make sure you do not miss seeing this beautiful and large cloister - especially when visiting in the hot and hectic summer in Rome. This place is truly soothing and wonderful on a hot summer day. Also, because the Baths of Diocletian is not a major tourist hot spot, usually you will find fewer people - you can relax and take your time. And, of course, this cloister has many Roman antiquities on display that are worth seeing.


After entering the basilica and proceeding into the main section, turn to the right, and you will see a line of barrier posts arranged at an angle. These posts protect a series of long bronze lines and circles on the floor surface. These floor markings form the Meridian Line, which is a complex and very accurate sundial built in 1702, 140 years after Michelangelo transformed the interior of the baths into a basilica in the early 1560s.

Photo of the Meridian Line on the floor of the basilica of Santa Maria Degli Angeli e dei Martiri inside the 
Baths of Diocletian in Rome
Meridian Line on the floor of the basilica
Licensed from

Each day at noon, weather permitting, a ray of sunlight comes through a hole in an upper wall to shine a spot of light on the bronze lines in the floor. The location of this spot of light keeps changing over the course of a year.

Basically, the interior of the basilica was turned into a giant Camera Obscura. I show how it all works in my diagram below. The wall where the hole is located faces southwest towards the Sun moving from east to west during the day.

At noon, the Sunbeam effect happens, and the bright spot's position on the floor is observed. I show the angle and location of the interior Meridian Line on the floor of the basilica in relation to the Sun's daily trajectory across the sky.

Diagram showing the location of the Meridian Line within the Baths of Diocletian and also showing how the Sun 
aligns at noon with a hole in the wall
How the Meridian Line works and its location
Original photo courtesy of Google Earth


The story of how the Meridian Line came into existence provides an intriguing look at Italian politics during that part of the Renaissance. In the year 1700, Italy was not a united country - it was composed of several competing states and cities.

Furthermore, even though the two cities of Rome and Bologna were both a part of the Papal States, there nevertheless existed a rivalry between them.

When the city of Bologna commissioned Giovanni Cassini in 1653 to create a meridian line inside the city's grand cathedral of San Petronio (shown below), Pope Clement XI felt compelled to do the same. To him, it was important that Rome, the heart and soul of the Church and the Papal States, also should have a meridian line that was even more significant than the one in Bologna.

Two photos together showing the outside of the Basilica of San Petronio and the 0 line inside
The first meridian line in Italy
Basilica of San Petronio in Bologna and its Meridian Line
Image courtesy: Dimitris Kamaras - CC by 2.0

And thus, in 1700, the Pope commissioned a true "Renaissance Man," Franceso Bianchini (shown below) - architect, astronomer, and mathematician - to build a great meridian line inside the basilica within the ancient Baths of Diocletian.

Clement XI stated that a meridian line was required to show how the Gregorian Calendar, which revised the ancient Julian Calendar, was superior to the ancient, pagan calendar. Also, having such a complex sundial in Rome would allow the Church to calculate the yearly date to celebrate Easter accurately. The only difference between the two calendars was that the year was 365.25 days long in the Julian but 365.2425 days in the Gregorian calendar.

Engraving of Franceso Bianchini, Italian architect, who lived from 1662 to 1729 AD
Engraving of Franceso Bianchini 1662-1729 AD
Builder and designer of the Santa Maria degli Angeli Meridian Line


Seemingly, building a meridian line just to calculate when to hold Easter was extravagant, but it was truly necessary. Unlike Christmas, which is occurs on the same day every year, the date for Easter changes from year to year - it has to be calculated based on a formula, shown below:

Easter day is held on the first Sunday after the full Moon that occurs on or after the spring equinox. But ... if the full Moon falls on a Sunday the date changes and Easter is thus held on the next Sunday.

Did you understand all that? It is a bit confusing. The point is that the Meridian Line makes it simple to figure out when Easter should be held. I think another use of this device was to calculate when the winter and summer solstice, and the spring and autumn equinox would occur.

Another possible reason was the Catholic Church's desire to show how their precise Meridian Line, based on the Gregorian Calendar developed by Pope Gregory XIII in 1582, was superior to the Roman pagan system of time measurement. And, of course, the Papal authorities wanted to have a superior time instrument in Rome, the heart and centre of the Catholic church.

One of the main reasons why the basilica within the Baths of Diocletian was chosen as the location for the Meridian Line is based on its structure and age. Placing it inside a 1,400-year-old building guaranteed that all the walls and floors had settled so there would be no worries about shifting architecture - thus ensuring the Meridian Line would remain accurate.

Much time and expense were required to build and carefully calibrate the floor markings and wall hole. Therefore, any shifting of the structure could have serious implications. Seeing as how this Meridian Line still works perfectly after 320 years, I guess they chose a great location in 1700 for their amazing sundial.

Closeup photo of a detail of the Meridial Line on the floor of the basilica of Santa Maria Degli Angeli.  The photo shows 
a golden crab inlaid in the marble floor alongside numerical measurements
Closeup detail of the Meridian Line on the floor of Santa Maria degli Angeli
Licensed from

Apart from all the technical and propaganda reasons for the existence of this remarkable sundial, it can be appreciated simply for its beauty and artistry. The bronze lines and circles, in combination with the astrological markings and figures set within white marble, create a beautiful work of art, as shown in the photo above and below.

Many other Meridian Lines were built in Italy (Vatican, Milan, Florence, Palermo), France (Saint Sulpice), and even in England (Durham Cathedral).

The first attempt at building a Meridian Line happened in the basilica of Santa Maria Novella in Florence from 1572 to 1574. It was commissioned by Cosimo de' Medici, and Ignazio Danti designed it, but it was never finished; unfortunately, Cosimo de' Medici died before it was finished.

Photo showing a long view of the Meridial Line in the Basilica of Santa Maria degli Angeli in Rome inside the Baths 
of Diocletian
Still Working after 320 Years (1702 - 2022)
Image courtesy: Sharat Ganapati - CC BY 2.0

An interesting aspect of these Meridian Lines is how they are helpful in showing how much a building has shifted when the alignment of the Sun's light on any of the lines starts to become inaccurate. Also, a Meridian Line can be called a "Large Scale Gnomon."

It is splendid to see how this centuries-old technical and scientific creation in the basilica of Santa Maria degli Angeli e dei Martiri still works well and delights people every day. I am sure it will keep working fine for many centuries to come, barring a destructive earthquake or some other calamity.


A great museum of Roman antiquity exists in Rome, and it is called the National Roman Museum (Museo Nazionale Romano). This museum was created in 1889 and was initially centred in the Baths of Diocletian.

However, in more recent times, the museum has now spread to three additional locations in the city of Rome. Within the Baths of Diocletian "branch" of this museum, both ancient art and modern art are displayed in some of the surviving great halls and rooms within the baths, which are known as Hall VIII, Hall IX, Hall X, Etc.

Photo of National Roman Museum inside the Baths of Diocletian featuring a 
sculpture by Henry Moore and two ancient Roman sculptures
Ancient and Modern Art in HALL X of the Baths of Diocletian

The image above shows Hall X, which was one of the ancient grand entrances into the main baths building. The two ancient statues in the photo are part of the Tomb of the Platorini family that was reassembled in this room in 1911 after being moved from its location near a Roman wall along the Tiber river.

Most likely, the tomb was reassembled for an International Exhibition celebrating Italy's 50th anniversary of unification. Many of this exhibition's displays were held in the baths. The modern statue is a work by the British sculptor Henry Moore (1898-1986). More of his work is shown in the following two photos.

High quality photo of Hall XI within 
the Baths of Diocletian, part of the National Roman Museum, displaying sculptures by Henry Moore in 2016, photo by Linden Underhill
Looking towards the northeast end of HALL XI of the Baths of Diocletian
By special permission © Linden Gledhill

The splendid photos above and below show Hall XI within the Baths of Diocletian. This large hall measures 40 metres long (130 feet) by 11 metres wide (36 feet), and the former barrel-vaulted roof has been replaced with a new one.

In ancient times, this room was a cistern to store water for the large outside Natatio swimming pool. The inner walls of this extensive room were covered with a special mortar that made the whole room watertight.

However, archeologists believe this room was not always a cistern and may have had another purpose during the early years of these Baths. Probably, when the Baths began operating at full capacity, it was discovered that there was insuffient water flow to meet the requirements of the open-air and enormous Natatio pool.

Obviously, the Romans had to immediately begin convering this long room into a water storage area. The walls must be very thick to have withstood all that water pressure without buckling.

High quality photo of Hall XI within 
the Baths of Diocletian, part of the National Roman Museum, displaying sculptures by Henry Moore in 2016, photo by Linden Underhill
Looking towards the southwest end of HALL XI of the Baths of Diocletian
By special permission © Linden Gledhill

In the photo above, more abstract sculptures by Henry Moore are displayed. This photo conveys well the length and height of this ancient room used to store water so long ago. The roof and ceiling are not ancient. Unlike the Frigidarium, the roof of this structure did not survive. On the far right, some of the mortar that waterproofed the walls still clings to the brickwork along the bottom. In the background, you can see a large floor mosaic which is shown in greater detail below.

Photo of the floor mosaic inside Hall XI of the Baths of Diocletian showing the whole
mosaic with great lighting and perspective
Roman floor mosaic in HALL XI of the Baths of Diocletian
By special permission © Anton Skrobotov

Also in Hall XI is a large Third Century mosaic, shown above, which portrays Hercules and Achelous. However, this mosaic did not exist in the Baths of Diocletian during Roman times. Originally, this mosaic was in the Villa of Nero in Anzio. Placed in storage in 1931, it was only recently moved to its new location in Hall XI, where it is safe from the effects of Sun and rain. This mosaic is discussed further in the "Mosaics" section further down the page.

Photo of a colonnaded corridor within the 
Large Cloister (Michelangelo's Cloister) in the Baths of Diocletian complex and part of the National Roman Museum displaying 
ancient Roman statues
Museum statues on display in one of the four colonnaded corridors of the Large Cloister

Until the 1990s, many ancient sculptures were on display in various parts of the Baths. However, starting in 1998, most of the sculptures were transferred to the nearby Palazzo Massimo alle Terme, another branch of the National Roman Museum in Rome. Despite the transfer, many Roman sculptures remain on display in the Large Cloister and Halls of the Baths of Diocletian, as shown in the photo above and below.

Today, even modern art is displayed during various exhibitions within the Baths. Though the Baths of Diocletian focuses primarily on art that is ancient, contemporary art is also included, as shown earlier in photos of modern sculptures in Hall XI. Below is a photo of Hall IX, located in front of Hall X. This hall is not entirely roofed and houses partial sculptures and surviving pieces of architecture from the Baths of Diocletian.

showing various sculptures and architectural remnants inside 
Hall IX of the Baths of Diocletianof Diocletian
Inside HALL IX of the Baths of Diocletian
Licensed from Dreamstime

The museum first began in the Baths of Diocletian and then spread to other locations in Rome. Today, one of those locations is still within the baths, which houses two of the museum's branches:

•   The Museum of Written Communication in the Roman World;
•   The Museum of Protohistory of the Latin Peoples

Also, various Roman statues and other antiquities are spread around the various halls and other areas of the baths but not within the basilica. These areas are shown below in a map of the baths.

Guide to Baths of Diocletian showing
an overhead photo of the baths today with labels identifying the location of all the halls, museums, and church
Location of Museum Halls and Cloisters within Baths of Diocletian ruins

In my diagram above, just right of centre, you can see the location of the two museums labelled in yellow. To the left, the various halls displaying art are shown. The location of the two cloisters in relation to the basilica is shown, and you can observe how the Large Cloister takes up considerable space.

In the next section, the two museums listed above are explored. I will describe their purpose and what they are displaying.


This museum is located inside a 3-storey modern building just below the Large Cloister. Essentially, this is a museum that looks at thousands of ancient Roman inscriptions inscribed on a wide range of objects. These objects include plaques, sculptured reliefs, bricks, tombstones, pipes, and lamps - anything inscribed with ancient Roman writing that helps us to understand Roman life and culture.

photo of an ancient 
Roman inscription in the Museum of Roman Written Communication in Rome
Inscribed object in Roman Written Communication Museum
Image courtesy: Klaus Wagonsonner - CC BY-NC-ND 2.0

Just like people today, the Romans had many aspects to their lives beyond work and family. The thousands of inscriptions help us to understand and experience Roman humour, funerals, politics, religion, and various social aspects of their lives. And though this museum houses over 20,000 different objects, only 900 are on display.

This collection began in the late 1800s, and most of the items were discovered in and around Rome. The people who either inscribed the items or are mentioned represent a wide swath of Roman society - soldiers, plebians, patricians, slaves, senators, and even Emperors.

photo of ancient Roman metal codex and a few pages from 4th or 5th century and on display in the Museum of Roman Written
Communiations with the National Roman Museum in the Baths of Diocletian
Roman metal codex pages - 4th or 5th century
Image courtesy: Ryan Baumann - CC BY 2.0

Above are two photos showing a metal codex from the fourth or fifth century AD. Only three of the seven pages are shown. Each page is filled with writing and images on both sides. A metal cover protected the book, but only the back part is shown. The images show a bearded man and a woman in a robe as well as a cow or ox.

photo of ancient Roman hardcover book from the early fourth century AD called the 'Codex Sinaiticus'
Ancient Roman book "Codex Sinaiticus" 4th Century
76 × 34 cm (30 × 13.5 in) - Book Open
Public Domain

Though the Romans wrote mostly on scrolls, they also had hardcover books, just like today, which they called a Codex. Unfortunately, due to the ravages of time, virtually all Roman books have disappeared except for a few. Above is an example of an actual Roman book from the middle 300s that has survived in good condition.

The book is quite large and, when opened, is almost 80 cm wide (30") wide and 34 cm high (over 1 ft) high. It is fascinating that this book was written just a few decades after the Baths of Diocletian opened. This book is a copy of the New Testament from the early Christian church of the Roman empire. Unfortunately, this book is not in this museum. I included it simply because it is the best example of "Roman Written Communication" in existence, in my opinion. This book really should be in this museum.


This museum is located on the second floor of the Large Cloister colonnades. This museum, through archaeological exhibits of very early Latin culture, looks at the six centuries before the city of Rome was established. It explores the early history of the people inhabiting the vicinity of Rome and surrounding areas from the 11th century BC to the 6th century BC - a span of 600 years.

photo of a Roman and chariot 
bas-relief in the museum of Protohistory of the Latin Peoples in the Baths of Diocletian
Bas-Relief of a man and chariot
Licensed from

So many of the museums in Rome focus on Roman history that began with the Roman Republic in 509 BC or the Roman Empire that began in 27 BC. However, the Museum of Protohistory of Latin Peoples looks at the 600 years before the Romans - as a city or nation - existed. The museum explores the political, religious, economic, and social structures of those people who lived in ancient Latium - the area of central western Italy where Rome is located. These people of Latium are also known as the "Latin Peoples."

photo of a relief from the Museum of 
Protohistory of the Latin Peoples in Rome
Relief from Museum of Protohistory of Latin Peoples
Image courtesy: Klaus Wagonsonner - CC BY-NC-ND 2.0

If you are interested in knowing more about where the Romans came from and how they grew into such a powerful and huge empire, then these two museums are a must. Together, the "Written Communications" and "Protohistory" museums have thousands of inscriptions and artifacts on display. Examples of the artifacts are statues, weapons, shields, tools, bronze and iron implements, pottery, marble reliefs, and art.


photo of western side of Baths of Diocletian 
showing the Clemintino Granary with Octagonal Hall on the left and entrance to Basilica of Santa Maria degli Angeli on the right
Western Side of Baths of Diocletian
Octagonal Hall - Clementino Granary - Basilica Entrance
( Far Left to Far Right)
Image courtesy of East VR - Educational

Today, those Halls and other rooms of the Baths of Diocletian that are not part of the Basilica are used to display ancient and contemporary art. Of course, this was not always the case - in the ancient past, these halls were used to store water or as changing rooms or grand entrances to various parts of the Baths.

After the baths closed after 537 AD, these large rooms and halls remained empty and no longer served a function. However, after a thousand years, these rooms found a new purpose because they remained structurally sound, and some of them still had their original roofs.

In the year 1566 AD, one of the halls was used to store grain by Pope Gregory XIII to feed the growing population of Rome, which had tripled during the 16th century from 30,000 to almost 100,000 people. In fact, by the early 17th century, nearly all the halls were used to store grain. Furthermore, because Pope Gregory XIII had started the process, the granaries were referred to as the Granari Gregoriani.

photo of latin inscription above doorway to 
Clemintino Granary on wests side of the Baths of Diocletian
Inscripton above doorway - Western side of Baths of Diocletian
"The providence of the Best Prince
Clement XIII Pontifix Maximus (Pope)
The Conservation of Oil Production
He established Olive Oil Rationing in 1763"

The photo above shows one of the main grain storage areas, which was known as the Clemintino Granary. This was in operation until 1816, at which time it was converted into an orphanage and poorhouse for women run by a charitable organization called the Istituto Romano di San Michele.

After 1870, the name changed to Orfanotrofio Communale di Termini until 1928, when it reverted to its original name. Today, this part of the baths is still owned and operated by the Istituto Romano di San Michele which is an organization that dates back to 1582 when it was founded by Pope Sixtus V.

Thus for two centuries, the large halls of the Baths of Diocletian were repurposed for grain storage. Under Pope Clement XIII, in 1763 AD, several of the halls were also used to store oil in order to assure a constant supply during times of shortage. The Octagonal Hall, shown below, is located on the far left side of the Baths. It was used as a bakery for many years in addition to becoming an oil storage facility after 1763.

Photo of the exterior of 
the Octagonal Hall of the Baths of Diocletian showing two sides of the structure clearly in year 2017
Former rotunda is now the Octagonal Hall used to display sculptures
Image courtesy: Jamie Heath 2019 -
CC BY-SA 2.0

The halls you see today on the eastern side of the baths complex today had to be restored to their ancient and ruined condition - they were not renovated to look like they did when they were pristine and covered with shining marble. Actually, there is always an ongoing program of stabilizing and restoring the whole baths complex. For example, Hall X, also known as the Aula Decima, underwent 30 years of restoration.

Hall XI, the Cistern Room, where water was stored to help feed the massive outside Natatio swimming pool, has also undergone extensive restorations. This long room with high ceilings has changed so much over the centuries. In ancient times, it began possibly as a changing room (Apodyterium) that was soon converted to water storage (cistern). Then, in more recent centuries, it served as a grain storage area before its current use as a room to display ancient and modern art. It is thought this room once had a long barrel vault ceiling; however, the ceiling seen today is of a more recent construction. I assume that the old ceiling must have collapsed at some point in time.

Three domed halls or rooms have survived. The first, the smallest, is seen right after entering the basilica within the Baths of Diocletian. The second is the Octagonal Hall on the far western side of the main baths complex and basilica. The third domed hall, another large rotunda, is located at the extreme northwest corner of the baths complex.

This rotunda was once part of the extensive wall that surrounded the whole grounds of the baths. It had a twin at the opposite corner that is mostly ruined. It is likely that these rotundas were entrances designed to accommodate the heavy foot traffic that would enter the baths every day.

Photo of the exterior of 
the church of San Bernardo alle Terme in year 2011
Rotunda near the exedra became San Bernardo alle Terme church
Image courtesy: Jonathan Rieke - CC by NC-2.0

These rotunda halls - round, cylindrical rooms with a roof and a dome with a hole for light in the centre - were very grand and large and similar to the Pantheon's rotunda but only half its size. The picture above is of a Baths of Diocletian rotunda hall near its large exedra/theatre that survived mostly intact. It is now known as the church of San Bernardo alle Terme (St. Bernard of the Baths).

The ancient Roman rotunda, located at the southwest corner of the baths complex, was converted into a church from 1596-1598 by the Cistercian order and dedicated to St. Bernard of Clairvaux. The photo below shows the beautiful coffered dome - nine rows of coffered recesses that get progressively smaller.

Of course, this rotunda was restored and renovated extensively over the centuries, most notably the beautiful ceiling, which is not ancient. An extensive restoration was undertaken in 1670. I would describe this ceiling as a very elaborate and ornamented "Rococo" version of the Pantheon ceiling.

The number of coffers is rather extreme and they extend right up to the very edge of the oculus in the centre. Also, interestingly, there is an indentation between the intersection of each coffer, creating a very "busy" ceiling indeed. This is highly typical of the Baroque, and especially the more extreme Rococo periods of architecture in the 1600s and 1700s.

Photo showing most of the interior dome
of the church of San Bernerda alle Terme in Rome
Interior dome of San Bernardo alle Terme church - 2010
Image courtesy: Fr Lawrence Lew, O.P. - CC BY-NC-ND 2.0


One of the most interesting aspects of the story of the basilica within the baths has to do with its entrances and the "flow" of the church. A lot can change over the centuries, and some aspects of the basilica were definitely changed. First, I will discuss the changing main entrance to the basilica and its appearance. Later, in the next section, I will discuss how they boldly changed the direction of the church from right-left to down-up - a fascinating story.

Anyone familiar with the main entrance to the basilica inside the Baths of Diocletian will not recognize the structure on the left side of the photo below (with the green doors). Incredibly, from 1749 to 1911, that is what the basilica entrance looked like. Moreover, the further back in time one goes, the more drastic the change in appearance becomes. It is almost as if people just could not leave this poor entrance alone.

colour photo from the 1890s of the entrance area of the basilica within the Baths of Dioceltian showing how the 
entrance area to the church looked before  the 1911 AD alternation
Basilica entrance area in the 1890s before the 1911 alteration
Public Domain

Over the centuries, entrances to this basilica within the vast Baths of Diocletian have appeared, disappeared or have been reassigned. For example, dating from when the baths opened in 306 AD, the current main entrance was just a doorway between two different areas of the baths. And, then, 1,000 years later, in the 1560s, it was turned into a side entrance to the basilica from outside for two hundred years. I go into greater detail about the changes to this entryway below.


When the Baths of Diocletian first opened with much fanfare and celebration in the year 306 AD, the current basilica's main entrance was just a doorway in the rear of the Caldarium (hot) section of the bath that led into the Tepidarium (warm) section with its domed roof. However, after 99% of the Caldarium building was demolished in 1587 AD, all that remains today is a semi-circular wall section containing two doorways. My diagram below shows the "evolution" of this doorway from the year 306 AD to its last significant change in 1911. The sixth image (1911) is how the entrance looks today - this is also how you enter the basilica inside the baths.

diagram showing the six changes to the caldarium entrance area to the Basilica of Santa Maria degli Angeli e dei Martiri in 
the Baths of Diocletian during the years 306 AD to 1911 AD
The changing Caldarium entrance area to the Basilica in the Baths of Diocletian from 306 AD to 1911 AD


The entrance seen and used today came into being in the year 1911 when the city of Rome was preparing for a world exhibition celebrating the 50th anniversary of the Unification of Italy. They also wanted to display their great ancient Roman heritage proudly. Thus, there was a desire to return this entrance to some semblance of its ancient Roman appearance.

Thus, they chiselled away the 1749 version of the entrance and - today - we are left with a round, concave wall section from the former Caldarium and this curved wall is made of crumbling ancient brick and concrete. On a personal note, I like this entrance. I would have preferred they had left Michelangelo's restored Caldarium alone - he wisely left the round porch area unrestored as a reminder that people were entering a former and glorious ancient Roman ruin.

Anyhow, the two alternating images below show the 1749 AD entrance (photographed just before its demolition in 1910) changing to the current 1911 entrance (photographed in 2014). Quite a dramatic change, I must say.

photo of the entrance to the Basilica of Santa Maria degli Angeli e dei Martiri in the Baths of Diocletian 
in the year 1910   photo of the entrance to the Basilica of Santa Maria degli Angeli e dei Martiri in the Baths of Diocletian 
in the year 2014
Basilica entrance in 1911 versus 2014
2014 image courtesy of David Bramhall

And so, today, when you enter the basilica inside the Baths of Diocletian, you are passing through a doorway within a curved, concave wall that is the only remaining part of the baths' former Caldarium area. So, basically, what you see when you look at the current entrance is two doorways set within a concave semi-circle wall of ancient brick that looks old and crumbling.

In the 1910 AD photo, look for a small tower with a dome above the entrance with a crucifix on top. The tower is now gone, but the crucifix still exists and has been moved to atop the main hall of the basilica, as shown in this image.

And whereas Luigi Vanvitelli, the respected Italian architect of the 1700s, supervised the creation of the 1749 AD entrance changes, the 1911 AD entrance changes were done under the supervision of Italian archaeologist Rodolfo Lanciani (1845-1929). Next, I will discuss how the basilica "changed direction" in 1749 AD, the same year they made the side entrance the main entrance.


Around the year 1746 AD, the whole flow of the basilica, as designed by Michelangelo in the 1560s, was altered when its Nave - the main hall - was changed from horizontal (right to left) to vertical (bottom to top). The diagram below shows Michelangelo's plan and the "flow" of the church that his plan created.

diagram showing the floorplan and entrances of the 
basilica of Santa Maria degli Angeli e dei Martiri inside the Baths of Diocletian in the year 1561 AD
Michelangelo's plan and main entrance locations 1561 - 1749 AD
Main image courtesy of Google Earth

In 1561, Michelangelo's plan for transforming the frigidarium and tepidarium of the Baths of Diocletian into a church envisioned a long central hall (Nave) with an entrance at either end. Michelangelo's main entrance was located in the southeast so that, after entering and passing through a room, you would see the whole length of the main hall with its high ceilings and columns. At the end of the hall was the main altar with another entrance/exit behind the altar area that faced northwest. There was also another side entrance along the bottom (today's main entrance). And then, it all changed in the 1740s AD when Clemente Orlandi was commissioned by the Carthusian Monks to make changes to the basilica. Those changes are shown in the following diagram.

diagram showing the floorplan and entrances of the 
basilica of Santa Maria degli Angeli e dei Martiri inside the Baths of Diocletian in the year 1749 AD
Vanvitelli's plan and main entrance location 1749 to today
Main image courtesy of Google Earth

As you can see, there was a dramatic change to the "flow" of the basilica. After 200 years, the whole length of the basilica, the former nave, from right to left in the diagram, was transformed into a very long and huge Transept. Also, an extension was added to the basilica (in line with the main entrance) - this was made by busting through the Natatio facade in order to build a Presbytery and choir area.

While Clemente made the initial designs for the presbytery, it was actually completed by Luigi Vanvitelli in 1749 AD. Another change Clemente made - which is not shown in the diagrams - is how he filled in two large arches - one on each side of the entrance to the former Tepidarium, where today's main entrance is located. The effect of that change was to block the light coming from the large Roman windows along the southern outside wall. The image below shows the change to the windows by comparing a 1569 AD sketch to a 2019 AD photograph.

Two images showing the interior of the Basilica of Santa Maria degli Angeli e dei Martiri in 1569 AD and then 
in 2019 AD to show the great changes that happened and which seriously changed Michelangelo's efforts.
Michelangelo interior in 1569 AD versus Vanvitelli Clemente interior in 2019 AD

As the images above show, the "spartan," big window look achieved by Michelangelo when he transformed the frigidarium of the Baths of Diocletian, has been seriously altered. The interior of the basilica changed radically from a rather plain and austere appearance with large windows, starting in the 1560s, to a very ornate "Late Baroque" architectural style in the 1740s.

Outside light now comes in through smaller upper windows only. I like the baroque look, and in my opinion, Vanvitelli did a tremendous job. I like the good symmetry between columns and entablature. Notice how he added great detail around the large arch and in each upper window area, in addition to the ornate entablature above the columns and the inlaid marble floors. Furthermore, he added that same beautiful detailing to every arch inside the basilica. I think the ancient Romans would approve of this display of architectural splendour.

The architectural changes by Clemente Orlandi before 1749 were considered a travesty by many people. However, notwithstanding how people felt about his alterations to Michelangelo's work, the deed was done, and the main entrance was moved to the former minor side entrance. The other former entrances were walled in, and the room they were located in was closed. Instead of entrances on either side of the new transept, there were chapels on either side of a rather long transept that some consider disproportionate in relation to the nave of the basilica.

Luigi Vanvitelli, in a demonstration of his considerable architectural skills and sensibilities, made the best of a bad situation. He added extra columns (false columns), and above them he also added extra entablature that went all around the basilica interior. Furthermore, he finalized the addition of eight huge paintings from St. Peter's and other rich decoration - in effect transforming Michelangelo's more spartan and austere interior into a sumptuous "Baroque" interior, as shown in the image above.


When you look at the diagram below, you will notice something rather strange. The basilica you see and enter today is marked in orange. Now, look around that orange - look at all those rooms (marked in green). I count 13 of them, and they are actually vast and barren rooms and halls that surround the main basilica interior. That is a lot of space. What is their purpose today? Are they being used, or are they just gathering dust? Can one visit these rooms? As far as I know, the rooms are not being used, and access is blocked. I imagine you would probably need special permission to visit them.

diagram showing the 
room surrounding the footprint of the basilica inside the Baths of Diocletian today
Rooms surrounding footprint of Basilica within Baths of Diocletian

When you enter the basilica, you are seeing only half of what is in that building - the rest is hidden from the public. I am guessing that, perhaps, the church uses these halls to store things. But I cannot say for sure because I was not able to find any information on their current usage. When I return to Rome, I will see if I can get permission to explore these rooms and take pictures which I will post here. I will try to peek into every one of those rooms and end the mystery.

It is interesting how, in the 1560s, there was a plan to turn these halls into 14 chapels - seven devoted to the seven angels of the vision that inspired the basilica (Largus, Smaragdus, Cyriac, Sisinnius, Trasonius, Marcellinus, and Saturninus) and seven more chapels devoted to Christian martyrs. Doing that was a reasonable plan because the name of the church in English is "Saint Mary of the Angels and Martyrs." Anyhow, that plan was abandoned in favour of Michelangelo's design.


Over 110 years ago, during the great Exposition of 1911 in Rome, those rooms surrounding the basilica were put into action. Basically, the Baths of Diocletian became a huge pavillion, and all these rooms were used to display Roman art and architecture. As shown in the diagram below, each room was dedicated to a different region of the ancient Roman Empire, such as "Hispania" (Spain), "Gallia" (France), etc. And they also unblocked the former main entrance that was used from 1561 to 1749.

Guide to 1911 International Exhibition in Rome held in Baths of Diocletian - this is just a part of the guide with 
additonal helpful information text in gold by myself.  This diagram shows how the many vast and barren ancient rooms and halls
surrounding the basilica of Santa Maria degli Angeli e dei Martiri were all used to display anciennt Roman artifacts during the 
1911 Guide to Exhibition inside the rooms surrounding the basilica in the Baths of Diocletian
Courtesy of the American Academy in Rome, Library.

Because these rooms were used for an exhibition seen by hundreds of thousands of visitors, they had to be in good condition. Perhaps restoration work was done before the exhibition to make them safe and stable. However, that exposition was held over a hundred years ago. Nevertheless, I am guessing the rooms are still in good condition, and visitors could enter them if access were allowed.

An interesting fact is that, for several decades, from the 1870s to 1911, an American sculptor lived in one of those rooms - until he got thrown out. That fascinating story is shown in a "Did You Know?" segment just below. The fact that someone lived in those rooms before the 1911 Exhibition for decades indicates one or more of these rooms were in reasonable condition.


Just like the Baths of Caracalla, these baths had many mosaics, some of which have survived, some partially and others whole. These mosaics, known as "Opus Tesallatum" to the Romans, are images made by assembling thousands of small tiles together that were bound to a surface with mortar. The tiles were tiny, about .5 cm (.20") in size and made from materials such as stone, marble, pottery, and glass. Much work and skill were required to create these works of art that have lasted for so many centuries. Roman mosaics are important because they show us glimpses of Roman life and culture.

The first mosaic shown below is stunning and colourful. It is the image of Medusa, the snake-headed Gorgon monster with snakes coming from her head. Ancient mythology says her gaze could turn you to stone. She has often been depicted in films and even video games. This was a floor mosaic, not a wall mosaic, and the whole mosaic was actually much larger than the part shown in the photo below, which you can see in this image (click to view).

mosaic of a medusa from the 
Baths of Diocletian
A beautiful mosaic of the legendary "Medusa"
Licensed from Dreamstime

mosaic of a woman from the Baths of Diocletian   mosaic of a rooster from the Baths of Diocletian
Rooster photo Anthony Majanlahti - CC BY-2.0

And above, on the left we have a mosaic of a woman with an elaborate headdress, and a rooster on the right. Chickens were very important to the Romans because these birds were used as "auguries," a way to tell the future. A Roman priest would open a cage and scatter food before a chicken. If the bird ate with gusto and stamped its feet, that was a good sign. But if the bird ignored the food, that was a bad sign.

Believe it or not, it is said that the Roman Senate - and even Generals - often did not make decisions without first getting a "reading" from their extraordinary chickens. This blog article (click to view) further explores these "Sacred Chickens," with a good story about a Roman sea commander who, because he ignored a bad chicken result, was later defeated in a naval battle.

floor mosaic in cistern room of the 
Baths of Diocletian
Huge floor mosaic of Hercules and Achelous
Hall XI - (Cistern Room)
Image courtesy of dvdbramhall

Interestingly, the floor mosaic above actually came from the Villa of Nero in Anzio,. The mosaic was created in the third century. Discovered in 1931 , this mosaic was in storage for many years until several years ago, when it was placed on the floor of Hall XI of the Baths of Diocletian.

The mosaic depicts the mythology of a battle between the gods Hercules and Achelous. In this mosaic, Hercules is tearing a horn from a bull, an animal shape that the river god Achelous took. The ripped-off horn becomes the Horn of Plenty, also known as a Cornucopia. The size of this work is quite large, measuring 80 sq metres (860 ft) in width and length. Once again, the amount of work and artistry required to produce this large mosaic is very impressive.


When Michelangelo first entered the Baths of Diocletian to begin making plans for a basilica inside the Frigidarium, what did he encounter? How damaged were the ruins of the ancient baths? Undoubtedly, he saw a vast hall with floors thick with mud and debris, and damaged walls stripped down to brick and concrete.

But he also would have seen a vaulted roof and many columns that were still in place. He would have seen great possibilities and strong indications that the ruins could indeed be reused and adapted successfully to design a basilica from the decaying structure.

It is said that Michelangelo loved great challenges, and, at the age of 86, he certainly faced one of the greatest endeavours of his life. He was already involved in the creation of St. Peter's, and he had finished making the model for its dome. Fame and money were not always his main considerations when undertaking a new commission. Converting the ancient ruins of the largest Roman baths ever built into a 16th century basilica would have tested his abilities greatly - a tremendous goal to achieve.

Santa Maria Degli Angeli e dei Martiri basilica 10 years before construction began in 1551 AD
Baths of Diocletian Main Hall in 1551 AD
Looking southwest towards Natatio facade
Engraving by Hieronymus Cock 1551 AD

The images above and below are engravings showing the Baths of Diocletian's Frigidarium main hall in the year 1551 AD, ten years before work began on converting the ruins in 1561 AD. This is what Michelangelo would have seen before his work began on the basilica. The vaulted ceiling and large columns supporting it are still standing. The capitals and parts of the entablature have also survived above the columns.

Baths of Diocletian interior in 1551 AD showing the Main Hall before the church of Santa Maria degli Angeli e 
dei Martiri was built inside the ruins.   It shows how the original vaulted ceiling and columns survived.
Baths of Diocletian looking northwest
Courtesy of Lawrence OP - 2019 -

However, you will also notice that a lot of dirt and mud has entered the building, and the walls are cracked and stripped of all marble and decoration. In addition, all the large windows are bare - any glass covering them has vanished after almost 1,250 years in 1551. The image above shows the degree of decay. The top of the ruins is covered with vegetation, and the area in front of the ruins is heavy with rubble and piles of dirt. These baths might have collapsed without the intervention and restoration in the 1500s, .

Below are two alternating views of the basilica of Santa Maria degli Angeli e dei Martiri. The first image is an engraving from 1760, followed by a photo of the same view 260 years later in 2020.

image of Baths of Diocletian church in the year 1760 AD Google earth image of Baths of Diocletian church in year 2020 AD
Baths of Diocletian church in 1760 compared to 2020 AD
Engraving by G.B. Piranesi, British Museum CC NC-SA 4.0
Photo courtesy of Google Earth

There have been several changes over the last three centuries. The old engraving shows a wall in front of the baths that no longer exists in the 21st century. The windows have gotten larger and longer. Also, they removed the steeple from the dome of the Tepidarium entrance area. Furthermore, there are now a lot more trees and less mud. I am sure Michelangelo would be pleased that his basilica within the Baths of Diocletian still stands 500 years later. However, he would probably be less pleased by the renovations to his work and vision by the Italian architects Clemente Orlandi and Luigi Vanvitelli in the mid-1700s.


Below is a listing of all the main historical changes to the Baths of Diocletian since it opened in 306 AD, including changes to the basilica of Santa Maria degli Angeli e dei Martiri since its completion in 1564 AD.

 298 AD  •  Construction begins.

 306 AD  •  Baths open.

 537 AD  •  Baths closed due to loss of water supply (aqueducts destroyed by Barbarians).

1561 AD  •  Michelangelo begins the process of transforming the Frigidarium and Tepidarium areas of the baths complex into the basilica of Santa Maria Degli Angeli e dei Martiri (St. Mary of the Angels & Martyrs). Charterhouse construction for Carthusian Monks began.

1564 AD  •  Basilica within Frigidarium and Tepidarium is completed.

1565 AD  •  Large Cloister designed by Michelangelo construction begins.

1566 AD  •  Pope Gregory XIII authorizes a hall in the western baths for grain storage.

1575 AD  •  Several halls are converted to Grain and Oil storage and workshops, which lasts until 1889, when the National Roman Museum is established to display several collections of ancient Roman sculptures and other artifacts.

1600 AD  •  Large Cloister completed.

1676 AD  •  Second Floor added to Large Cloister.

1695 AD  •  Central fountain added to Large Cloister.

1705 AD  •  Pope Clement XI has a bakery built in the Octoganal Hall rotunda, and additional granaries are added.

1746 AD  •  Italian Architect Clemente Orlandi (1694-1775) closes both entrances at either end of the basilica, leaving only the side entrance facing the former exedra (today's Piazza dell Repubblica). Effectively, he turns the former nave into a transept. After closing the main southeast entrance, he constructs the Chapel of Niccolo Albergati in honour of a Cardinal. When you enter the basilica, this chapel is on the right side of the transept. He designed the Presbytery expansion.

1749 AD  •  The Carthusian monks commission Italian Architect Luigi Vanvitelli to further modify the basilica and correct some of the architectural ideas implemented earlier by Clemente Orlandi.

Vanvitelli finishes placing the large Vatican paintings seen on the walls of the main basilica. He also creates arches leading into the chapels, and he provides a unifying and rich decoration to the walls, floors, etc. In addition, he builds eight new columns that, although they resemble the original columns, are actually made of just brick covered with plaster and then painted.

He provides a unifying entablature (horizontal decorated beams above columns) structure throughout the church. He also modifies the concave main entrance to the basilica so that it has pilasters, horizontal fasciae, and a tympanum over the doorway. Finally, he completed the Presbytery and the choir area built through the Natatio facade wall. By the time Vanvitelli has finished, the basilica has been transformed into a Late Baroque style structure, in contrast to Michelangelo's more austere approach.

1763 AD  •  Pope Clement XIII authorizes the storage of olive oil in the baths.

1816 AD  •  Pope Pius VII converts the Baths' west-side granary into an orphanage and poorhouse for women that is known as the Istituto Romano di San Michele.

1870 AD  •  After Rome becomes the capital of a united Italy in 1870, the name of the orphanage and poorhouse of the Baths of Diocletian is changed to Orfanotrofio Communale di Termini.

1878 AD  •  Via Cernaia street is built through the northwestern section of the Baths complex.

1884 AD  •  Charterhouse closed, and Carthusian Monks leave.

1889 AD  •  National Roman Museum opens.

1889 AD  •  Sections of the Baths are reinforced.

1908 AD  •  Most of the Charterhouse is demolished.

1911 AD  •  The Vanvitelli facade covering the main entrance to the church is demolished, and the concave Caldarium wall entrance seen today, with its rough brown brick, is developed. This was an effort to return the baths to their ancient Roman origins for the 1911 International Exhibition of Art in Rome.

1920 AD  •  Pope Benedict XV gives Minor Basilica status to the Santa Maria degli Angeli e dei Martiri church within the Baths of Diocletian.

1928 AD  •  Octagonal Hall is converted into a Planetarium which uses the large dome to display astronomy.

1987 AD  •  The Planetarium is closed.

1991 AD  •  Octagonal Hall is restored to its former, ancient condition, except for the dome lattice-work added for the planetarium, which remains.

2008 AD  •  Renovations and restorations begin in the National Roman Museum within the Baths of Diocletian. Previously inaccessible areas, such as the Small Cloister and surviving section of the outside Natatio pool, are renovated to allow visitors. Also, a richer multimedia and educational experience is developed for visitors to the Baths of Diocletian.

2014 AD  •  After six years, renovations to the National Roman Museum are completed at the cost of 6.5 Million Euros. The completion of these renovations coincides with the 2,000-year anniversary of the death of Emperor Augustus in the year 14 AD.


Getting to the baths complex is easy. The Baths of Diocletian complex is located beside Rome's central train station (Termini), which also has a subway "Metro" stop connected to both Metro Lines A and B. In addition, many city buses also stop at the train station. When standing directly in front of the basilica entrance, Termini train station is on your right, and the Piazza della Reppubblica is directly behind you. Once you reach the baths, you can then spend a fascinating few hours exploring the ruins, basilica, museums, and beautiful cloisters within.

Although some parts of the ancient baths are now gone, the vast ruins, thick walls, and existing spaces are still very impressive. Furthermore, the museums within the baths' various ancient halls and cloisters contain many beautiful statues, ancient engravings, and other interesting objects from the ancient Roman world.

Be advised that there are no cafes or restaurants inside the museum, so eat before you arrive. There are acceptable toilet facilities within the museums, and the whole complex is kid-friendly, especially the Large Cloister with its wide-open spaces, old cypress trees, and large carved animals that children find fascinating.

Nearby the Baths of Diocletian is the Piazza dell Repubblica, the Piazza Venezia, another branch of the Roman Museum located in the Palazzo Massimo with its stunning display of Roman sculptures, the Monti District, and the Vittorio Monument.

The map diagram below shows the Baths of Diocletian location relative to the central Termini train station in Rome. When the basilica of Santa Maria degli Angeli e dei Martiri is open, some areas of the baths and cloisters are free to visit. At other times, you will need to purchase a ticket for about 10 Euros, which is a good deal because this ticket entitles you to visit the three other museum locations associated with the National Roman Museum (Museo Nazionale Romano). The other three locations are:

 •  Palazzo Massimo alle Terme;
 •  Palazzo Altemps;
 •  Crypta Balbi.

In 2022, the baths and museums are closed on Mondays and holidays. Visiting hours are from 9 am to 7:45 pm. Be advised that if a special exhibition is happening in the baths, the ticket cost increases by a few euros.

The Palazzo Massimo all Terme is very close to the baths (red circle on map below). Again, standing directly in front of the basilia entrance, turn right, and the first building (3 storeys with a big central door) you approach is the Palazzo Massimo. The other two branches are much further away - 10 to 15 city blocks west of the baths, approximately (their locations are beyond bottom left corner of map below). All these other branches of the museum are packed with high quality Roman statues and artifacts. If you love seeing ancient Roman things, then you will really enjoy yourself.

Map diagram showing the footprint of the whole 
ancient Baths of Diocletian in 21st century Rome
Whole extent of ancient Baths of Diocletian complex superimposed over a photo of present-day Rome

This ends the Baths of Diocletian discussion, thank you for reading. If you have any comments, suggestions, or corrections, please email me.


The links below offer additonal information about the BATHS OF DIOCLETIAN, including entrance fees, hours, how to get there, etc.

A Tourist in Rome - Baths of Diocletian, part of the great "A Tourist in Rome" section at

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