During the Roman Empire, the art of stone flooring reached a new height of innovation. These masters of architecture were able to design a series of floors that actually glowed with toasty warmth from below, the first underfloor radiant heating system. This process made use of large tiles propped up on joists so that a gap was created beneath the surface of the floor. A furnace at one end of the floor and a vent at the other would draw heat continuously across the bottom of the floor warming it considerably. After the fall of Rome, the art of stone and mosaic flooring was largely lost to Western Europe and while these skills were preserved to some extent in Byzantium and throughout the Islamic world, it was many years before they reappeared in Europe.