The system utilized by the ancient Greeks was first found in the Temple of Ephesus in 350 BC. The Ancient Greeks termed this system hypocaust, which means “under burnt.” These pillars would have a layer of tiles above them which would be covered by a layer of concrete and then the floor tiles used for the building. A furnace would be lit and it would feed hot air and smoke into the space between the ground and floor of the building. In this way, the system could also be used to heat multiple floors of a building.