While the modern discoverers of these ancient Roman homes have done their best to preserve them, this was not the case in other eras. Scattered through the site are intrusions from the medieval era, when a cemetery was located atop the site and the deeper burials smashed right through the mosaics to construct their tombs. Ironically, these acts of vandalism are now also ancient historical sites well worth preserving, being well over a thousand years old themselves.
Roman homes were often heated by a hypocaust (literally "under-burn" in Greek): channels beneath a floor into which hot air was forced. The air then heats the floor, which keeps the rest of the house warm as well. Here we see those channels exposed by the breakages of the floor. Hypocausts are a really nice solution that is both efficient and comfortable, and they're occasionally used in modern construction by people rediscovering this architectural innovations---which is how I know that a hypocaust feels really nice on one's feet on a cold winter morning.