In ancient rome what was a hypocaust?

Answer 1

A hypocaust was the Roman heating system. There were hollow channels in the floors or walls of a house/building which allowed the heat from a furnace to flow through the house. Our present day central heating systems are based upon the same principles but with modern heat ducts and refinements.

Answer 2

Hypocaust was an ancient roman form of central heating. They would make walls and floors hollow and let steam and smoke go through the spaces to heat the surfaces. The Romans used it for heating the various rooms in their baths. In cold climates, they used it for central heating for their homes and some public buildings.