Cutaway diagram of a Roman hypocaust system (underground heating). Drawn by David Dobson © Canterbury Archaeological Trust Ltd Hypocaust From Wikipedia, the free encyclopedia Caldarium from the Roman Baths at Bath, England. A hypocaust (Latin: hypocaustum) is a system of central heating in a building that produces and circulates hot air below the floor of a room, and may also warm the walls with a series of pipes through which the hot air passes. This air can warm the upper floors as well. The floor has been removed to reveal the empty spaces which the hot. This dining room has a Roman underfloor heating system called a hypocaust, from the ancient Greek words hypo, meaning 'under', and caust, meaning 'burnt'.