Between the 2nd and 4th centuries AD, the heyday of the so-called Imperial Baths, hand-made bricks were used for most buildings in the Roman Empire (see Sardis).

So that we are fundamentally informed about how they are made, we will briefly let Leone Battista Alberti, a master builder from the Renaissance, have his say: "Bricks made from the same earth become much stronger when the mass, like bread dough, ferments and is cleaned of all the stones, even the smallest ones.

The bricks then become so hard when fired that they take on the hardness of a pebble when exposed to a large fire. And they get a hard crust, just like bread, whether from the fire when firing or from the air when drying. It is therefore advantageous to make them thin so that they get more crust and less pith."

Bricks and tiles were very popular building materials, as was pozzolan, a loose, earth-like material that was ideal for making mortar. The Roman builders were fond of mortar and especially cement. This led to the creation of Opus Cementitium, which played an important role in ancient architecture as concrete. But glass was also used. A mixture of quartz sand, lime and potash produced the first usable glass. Although this glass was not used very often because it was not stable enough for windows, it was often used in rooms where people wanted to make use of the warming power of the sun.

Most of the light openings and windows were simply completely open, which was what determined the seasonal opening times. In heated rooms, however, glass was used. As for marble, it should be said that it was often only used as external cladding for buildings, as it was a relatively expensive building material. Its use became more frequent as the Roman Empire developed and became more-wealthy.

The designs in thermal bath construction

The planning and implementation of construction work in the old Roman cities was not always easy. The small balnea and private bathhouses were relatively easy to integrate into the existing, extremely ill-considered cities such as Rome, which developed over time and were not built according to a complete original plan like Sardis or Perge, for example. However, the first problems arose with the large thermal baths. Building space was scarce and particularly hard to come by in the city centre and in the preferred locations.

As the thermal baths had to be as conveniently located as possible and still look prestigious, it was not always easy for the architects to build a dream thermal bath according to their ideas. The engineers often had to adapt to local conditions and more or less "squeeze" the buildings into gaps. Once the space problem had been solved, another problem arose: the water supply. Getting the water was not easy. But since the engineers of the time were not lacking in ingenuity, they managed to literally flood the cities with water.

Water, which was brought in with the help of countless aqueducts, could be distributed throughout the city. It was also the task of the emperors during their time in office to ensure an adequate water supply, as their reputation and standing among the people depended on it. At the time of the sack of Rome by the Goths in 410 AD, 11 aqueducts, 1212 fountains, 11 large imperial thermal baths and 926 public baths supplied the city. Never before had a city had such masses of water at its disposal. It is best to let a contemporary writer have his say on this. Pliny (23 AD - 79 AD) writes:

"But whoever sees the abundance of water so skilfully channelled into the city for public purposes - baths, houses, gutters, suburban gardens and villas; whoever considers the high aqueducts required to ensure its proper conveyance; whoever thinks of the mountains which had to be pierced and the valleys which had to be filled up for this purpose, will admit that the world has nothing more admirable to show."

The equipment of the thermal baths

For most bathing facilities, a basic division of the various rooms can be made. Bathers changed or undressed before starting the bathing process. The changing rooms (one bathed naked) of the ancient "swimming baths" were the so-called apodyteria (apodyterium). The apodyteria were often equipped with small benches running along the wall, which made it easier for bathers to change. The clothes that had been removed could be stored in small, lockable wall niches called loculi. In some large baths there was even an employee, the capsarius, who guarded the clothes.

The apodyterium was followed by the frigidarium, a mostly rectangular room that was never heated and whose pools, the piscines, contained cold water. There were also marble chairs in which one could have cold water poured over oneself. There are said to have been 1,600 of these marble chairs in the Caracalla Baths. It was also possible to have a massage. The frigidarium was usually the largest room in the thermal baths, towering over the others and often richly decorated. It is therefore not far-fetched to describe the frigidarium as the recreation room in the thermal baths. Parallel to the frigidarium there was often a large sports hall, called a palaestra or gymnasion.

In the palaestra people did sports before bathing. Finds show ball games, muscle and gymnastics exercises. But the sports we know from the Olympic Games and handed down from the Greeks, such as javelin throwing, wrestling, foot races and discus throwing, were also practiced. If you were exhausted after exercising, you could go back to the frigidarium and refresh yourself in the cold water. The tepidarium was connected to the frigidarium. It was a lukewarm room that was also called a passageway, transitional room or adjustment room between the cold and warm baths. There were rarely water basins in the tepidarium.

The room was relatively small compared to the other rooms in the thermal baths. People did not stay there for very long, usually only until their bodies had got used to the higher temperature. However, if there was no separate anointing room (unctorium) in the entire complex, the tepidarium could also take on this function. Once people had slowly got used to the higher temperature, they could continue bathing by entering the caldarium, which was the hottest room in the thermal baths.

The caldarium was always built facing south or southwest and provided with small niches in order to use the heat of the sun. It was always heated by a hypocaust system, which meant that the temperature on the floor could easily reach 50-60 degrees. For this reason, most bathers wore wooden sandals. The niches were provided with small tubs containing hot water in which people could take hot baths. It was also possible to have a bath attendant or a slave pour hot water over you.

If the thermal baths were very large, or if there was enough money available when they were built, there was often a separate sweat bath, the Laconicum. A small, round room, which in turn had niches in which one could sit down. As finds from the Thermae Stabiane in Pompeii show us, the Laconicum was obviously not heated with a hypocaust system, but with a charcoal oven, which produced enormous heat and was therefore more suitable. However, as already mentioned, not all thermal baths had this room.

If it was not available, the bathers had to make do with the heat of the Caldarium. Most bathers often use the Natatio after the hot bath or the Laconicum to cool off by jumping into the cold water. The Natatio was a large swimming pool, which was usually uncovered and facing north, so that the water was a refreshingly cold temperature. The following rooms were mostly only found in large, luxuriously equipped thermal baths and therefore require no further explanation.

As already mentioned in the case of the tepidarium, there was often a separate ointment and massage room where you could also be oiled. Massages were given by the in-house masseurs, or by slaves who had been brought along. There were also doctor's offices, where operations and dental treatments were also carried out from time to time. Of course, the doctors or balneologists (as they were also called) were happy to give advice on the bathing process and the sequence of rooms.

For relaxation, libraries and lecture rooms were often available in the larger complexes. Bathers thus had the opportunity to educate themselves in the libraries after bathing or to listen to a poet or philosopher in the lecture rooms before continuing their bathing. Finally, the snack bars, the rest areas and rooms and the gardens and green areas, of which there were often numerous, should be mentioned.

The heating and hypocausts of the thermal baths

The heating has already been mentioned in relation to the warm bath rooms, which were called hypocausts. The so-called hypocaust systems were heating systems that were designed to maintain the temperature in the individual rooms of the thermal baths. Hypocaust is Greek and means heated from below. Most of the thermal bath rooms had a floor that was built on supports made of bricks. This created a cavity between the floor and the actual ground. Hot air flowed through this cavity, which was generated in one or more central ovens using wood fires. Air ducts in the masonry, cleverly planned by the engineers, directed the hot air into the respective rooms.

These heating systems are roughly comparable to our modern underfloor heating. The ancient architect Vitruvius writes about this: "The suspended floors of the baths must be designed in such a way that a floor covering of 1.5-foot brick slabs is first laid, which is inclined towards the under-fire furnace in such a way that a ball thrown into it cannot remain inside, but rolls back to the heating chamber anteroom (preafurnium) of its own accord. This will make it easier for the flame to spread under the suspended superstructure. Pillars made of eight-inch bricks should be built on the paved floor, spaced at such a distance that 2-foot brick slabs can be laid on top of them. The pillars should be 2 feet high. They should be layered with clay kneaded with hair, and 2-foot-long brick slabs should be laid on top of them to support the screed."

Decoration and ornamentation in the thermal baths

The large, imposing rooms of the thermal baths were by no means bare and unadorned. The floors were covered with large, colourful mosaics, laid by specially trained mosaicists, whose outstanding skills often made them more durable than the buildings they decorated.

Today, the only mosaics you can often find are in the ruins of ancient bathing facilities. Mosaics were mostly colourful patterns, but also often depicted religious, imperial or hygienic ceremonies, which is why most theories about the bathing process and the processes in the baths are documented and justified.

They were also often found on the walls, especially in the hot, humid rooms, where they replaced the wall paintings, as these did not prove to be resistant to the unfavourable conditions.

Of course, there were also statues showing the respective emperor or the builder of the complex and of course images of gods. But not only individuals, but also entire events and groups were presented in sculptures and statues in the baths. The Lacoon group, for example, comes from the Trajan Baths and can now be seen in the Vatican Museums. Most of the sculptures were in the bathing area and were life-size. Colossal statues were also rare, such as in the Caracalla Baths, which even had seven examples. In the remaining rooms, where water and heat did not prevail, carpets could even be laid on the walls and floors. The often-numerous recliners were made more comfortable with animal skins.

The architects of the time were very good at designing and decorating the interior of the baths so that the individual works of art complemented each other and thus formed a single, large piece. Stucco ornaments and engravings played a major role in connecting the individual works.

Please read as well:

The Roman baths and ancient bathing

Tahtali - mountain of the gods of Greek mythology?

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• Roman Thermal Bath at Sardes Roman Thermal Bath at Sardes
• Roman Thermal Bath at Sardes Roman Thermal Bath at Sardes
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• Roman Thermal Bath at Sardes Roman Thermal Bath at Sardes
• Roman Thermal Bath at Sardes Roman Thermal Bath at Sardes
• Roman Thermal Bath at Sardes Roman Thermal Bath at Sardes
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