The heating system of the baths was based on the injection of hot air into the cavities, coming from the basement where the oven vents were located, known as praefurnia. A first cavity, called hypocaust, was created under the floor, which was suspended on brick pillars (suspensurae) placed on a pavement made of bricks. The walls were clad with a series of rectangular section terracotta tubes (earthenware tubes), known as tubules, which had side holes that allowed communication between the different series. These tubules were anchored to the walls by T-shaped iron grappas. Their arrangement allowed direct communication with the hypocaust, thus facilitating the transfer of heat upwards