The most impressive and the largest of the public baths in Ancient Rome were the Baths of Diocletian. They were built between 298 and 306 AD by Maxentius in honour of the emperor Diocletian, and although they were similar in structure to many other baths in Rome their immense size was a distinguishable feature. They were so vast, that they could accommodate around three thousand people. It has been argued that the main reason for building the Baths of Diocletian was to outshine the Baths of Caracalla, which is why they were made to fit twice as many people.
The Baths were composed of three main parts: caldarium, tepidarium and frigidarium. Besides the baths, the complex was made out of public spaces such as libraries, gymnasiums, theatre and gardens. The floors and cealings were adorned with fine mosaics and extensive use of marble makes up the interior of the baths while the exterior was made out of stucco resembling marble.
Today the remains of the Baths of Diocletian are proof of how grandiose these baths once were and how they shaped an everyday life of Romans. Today with help of technology, you can see visual restorations of how this majestic place once looked.
The three main parts of the baths are quite intriguing both in the way they were designed and the way they were used by the Romans at the time. Namely, the caldarium was a hot room which contained a hypocaust that provided heat from beneath the flooring. This was the main bath chamber, large in space and with dressing rooms on either side. The caldarium had the main bath filled with hot water and several more separate rooms which served as saunas or steam rooms. Along the sides of it were private rooms that had multiple functions, including private baths, poetry reading, reading and lecture rooms, etc.
In the large entrance hall was the tepidarium which provided baths with lower heat. Because there was so much natural light coming in into this space, it was filled with rich and complex decorative work. The frigidarium was the room with a cold water pool which was mainly used as a swimming pool or as a cold-water bath. Usually, frigidarium would be used after the hot water bath or exercising, as it was considered to be beneficial for closing the skin pores. On each end of the frigidarium were large shallow pools that were made for open-air bathing pools.
You might find the bathing rituals of Romans quite interesting, as they were the focal point of their social lives and recreational activities. Because Romans had built the aqueducts they were privileged to have enough water left after the usage for their daily lives, for their leisure time. As these Baths were places where people didn't come to get clean only, but rather a place where socialization and discussions about politics and daily matters happened, they were continuously being developed and improved in order to serve the social needs of the people. They also held theatrical and musical performances for the patrons to enjoy, and alongside all other amenities, there were food and perfume selling stalls. Believe it or not, there were even on top of it all, rooms for medical and dental procedures. Although there have been some changes, in many ways the Spa centres of today are much like those from the ancient Roman times.
After invading Goths destroyed the aqueduct in 537 AD and therefore had cut off the water supply that had been providing Romans with bath leisures, part of the decaying bath structure was later resurrected through a church of Santa Maria degli Angeli created by Michelangelo. This was the last structure Michelangelo has built, he was 86 at the time.
The rest of the remains of the Baths of Diocletian have been taken over by Museo Nazionale Romano, which has a goal of preserving and displaying the works of Ancient Roman art. Due to their meticulous ways of preservation and restoration, today you can see a collection of nearly 400 works of art and some parts of the ancient bath chambers.