The warm room or tepidarium was a mid-point in the baths, between the hot part and the cold part. This is a bigger room; only the apodyterium is larger. In this room, bathers would recover from the extreme heat (if they were coming from the caldarium) or from the intense cold (if they were coming from the frigidarium). Here, they could converse, get a massage, and even eat and drink.
The floor was connected underneath to the hypocaust from the caldarium in order to maintain a comfortable temperature. The ceiling consists of a barrel vault, with a south-facing gallery with three arches supported by columns where the paving is slightly raised. Considering the room’s size and layout, it would seem that the Capuchin nuns (the baths’ previous owners) used it as the convent’s kitchen.