Full of steam, the temperature exceeded the 30 degrees centigrade. Ideal to sweat and to take hot baths in the swimming pools which today do not exist. It is the room which is worst preserved, due to the damage caused by the previous constructions, in the past.
In the caldario there was a small swimming pool placed in the southeast corner of the room, which was rather shallow, and like in the Muslim Baths does not have steps of varying levels of access. The swimming pool was filled with hot water coming from the boiler that was passing through some lines that even today can be seen through the wall. A glazed canal that was built into one of the walls of the caldario was used to facilitate the circulation of hot air coming from the hypocaust.