Masada (Israel): Hypocaust Heating System in Bathhouse and Furnace Location

The caldarium (or hot bath) in Roman bathhouses was heated by raising the floor on short pillars (pillae) and circulating hot air heated by a furnace through the hollow spaces. In this bath house it appears that the steam was also forced behind the walls of the caldarium, or hot bath (the red clay-colored pipes on the wall). The opening was likely for an external furnace.