Tivoli the classical Tibur, is an ancient Italian town in Lazio, about 30 km east-north-east of Rome, at the falls of the Aniene river where it issues from the Sabine hills. The city offers a wide view over the Roman Campagna.
Gaius Julius Solinus cites Cato the Elder's lost Origines for the story that the city was founded by Catillus the Arcadian, a son of Amphiaraus, who came there having escaped the slaughter at Thebes, Greece. Catillus and his three sons Tiburtus, Coras, and Catillus drove out the Siculi from the Aniene plateau and founded a city they named Tibur in honor of Tiburtus.
- Villa Adriana, part of the UNESCO World Heritage site list from 1999
- Villa d'Este, part of the UNESCO World Heritage site list since 2001
- Villa Gregoriana
- Rocca Pia, a 15th-century fortress built in 1461 under Pope Pius II to counter the urban strifes between the Colonna and Orsini
- Temple of Vesta
- Temple of "Tiburtine Sibyl" (true dedication unknown). It was built in the 2nd century BC on an artificial platform in the acropolis. Characterized by Ionic columns (only two of which remain today), it measures 15.90 x 9.15 m. The interior was decorated by frescoes and stuccoes, now lost. A church, dedicated to St. George, is known to have existed in the temple from as early as 978 AD.
- Sanctuary of Hercules the Winner (2nd century BC). Now in ruins, it was one of the largest structures in central Italy at the time, and was located outside the ancient city, across the road leading to Samnium. Measuring 188 x 140 m, it included a theater, a large porticoed square and the temple. It was reached through a series of terraces, in a similar fashion to the Sanctuary of Fortuna Primigenia in Palestrina. The sanctuary also housed one of the more frequented council of musicians in Roman Italy.
- Cathedral of St. Lawrence (Duomo, rebuilt in 1635–40)
- Roman Temple of the Tosse, located near the Temple of Hercules and the Villa d'Este and dating perhaps to the early 4th century AD. It is a circular structure with a hole in the 12 m-diameter dome. In the 10th it was turned into a church dedicated to the Virgin Mary.