Is it ensure, insure, or assure?
town, Umbria regione, central Italy. The town is situated atop an isolated rock 640 feet (195 m) above the junction of the Paglia and Chiana rivers. An Etruscan and later a Roman city (in late Roman times it was called Urbs Vetus, from which its Italian name is derived), Orvieto was the seat of a Lombard duchy and of a Tuscan countship before becoming an independent commune in the 12th century. After much civil conflict and strife with neighbouring cities, the town passed under the dominion of the papacy in 1448.