In order to take advantage of solar energy and warm the caldarium, the baths face south-west. The caldarium was a warm room with a "floating" floor; the floor was elevated on pillars, with the space under the floor used as a heating well. It was in this way that the room can be warmed up. The caldarium in all the baths worked alongside the Frigidarium, the cold room, where the pool of cold water is located.
The Roman bathhouses were based on water brought to them via aqueducts. Roman aqueducts are artificial channels whose function was to transfer water from one place to another. In 537, the Goths destroyed the aqueducts that flowed to the baths causing them to cease functioning.
An interesting fact is that the ame of the railway station in Rome, Roma Termini station got its name from the baths.
One of the two towers of the baths is the church of San Bernardo alle Terme. One of the buildings of the National Museum of Rome is located in what was once the foyer of the bathhouse.
The baths were very popular in the rich and progressive empire of those days. Rome's elite class used to build baths in their homes and villas. Private initiators built public baths in the city's neighborhoods. These were established for business purposes and had entrance fees. In 33 BC there were no less than 170 baths in Rome, a number that has grown over the years.
Initially, these baths were a luxury that was only available to the rich, but there were attempts to make these sites accessible to those who did not have the financial means to gain access to the baths. This was the historical role of Marcus Agrippa, the Roman general who became the vicar of Augustus Caesar and became a governmental superintendent of Rome and an innovator. Among other things, he took care to supervise the public baths, inspect their heating facilities and ensure their order and cleanliness.
When Agrippa was rich and wise later on, he made an amazing gesture. He took upon himself the cost of the entrance fee to all the baths for the period of his supervision. He did it to let everyone in - both the rich and the poor. Later he also built the free baths that bore his name - the Agrippa Baths. This noble attitude towards the masses was unusual in the imperial days and made him a popular figure in the empire. A good shower was considered of great importance in those days!