The oldest artifacts found on the island may date to the late Paleolithic period. Important archaeological sites on the island are the Neolithic cave of Kagiani, probably a refuge for shepherds, the Neolithic settlement of Chalakies, and the extensive habitation of Thermi (3000–1000 BC). The largest habitation is found in Lisvori (2800–1900 BC) part of which is submerged in shallow coastal waters. There are also several archaic, classical Greek and Roman remains. Vitruvius called the ancient city of Mytilene "magnificent and of good taste". Remnants of its medieval history are three impressive castles.