Tivoli (tēˈvōlē) [key], Lat. Tibur, city (1991 pop. 52,372), in Latium, central Italy, on the Aniene River. An important tourist center, the city is beautifully situated on a terrace dominating nearby Rome and the plain to the sea. It is celebrated for the waterfalls formed there by the Aniene and for the Villa d'Este. An old settlement, Tivoli was conquered by Rome in the 4th cent. B.C. and became a favorite summer resort under the Empire. There are ruins of several Roman villas, notably that of Emperor Hadrian, and the well-preserved Temple of Vesta, which is now a church. The city also has a cathedral (12th cent; rebuilt 17th–18th cent.), with a fine Romanesque campanile.