From Etruscan times, the site, named Tibur, was the seat of the Tiburtine Sibyl. There are two small temples above the falls, traditionally associated with Vesta and the Sibyl of Tibur, whom Varro calls 'Albunea', the water nymph worshipped on the banks of the Anio as a tenth Sibyl to the nine mentioned by the Greek writers. In the nearby woods, Faunus had a sacred grove. During the Roman Age Tibur maintained a certain importance, also being on the way (the via Tiburtina, extended as the via Valeria) that Romans had to follow to cross the mountain regions of the Apennines.
An independent ally of Rome, which allied itself with the Gauls in 361 BCE, Tibur acquired Roman citizenship in 90 BCE and became a resort area famed for its beauty and its copious good water, and was enriched by many Roman villas. The most famous one, of which the ruins remain, is the Villa Adriana (Hadrian's Villa), but Maecenas and Augustus also had villas at Tibur, and the poet Horace had a modest villa. He and Catullus and Statius all mention Tibur in their poems. In 273 CE, Zenobia, the captive queen of Palmyra, was assigned a residence here by Aurelian.
There was further villa construction from the Renaissance onwards, the most famous of Tivoli's Renaissance villas being the Villa d'Este, begun in 1549 by Pirro Ligorio for Cardinal Ippolito d'Este.