This is a UNESCO World Heritage Site and a truly unique place. Although the villa is itself quite interesting, with some attractive frescoes on the ceilings, the main reason for visiting here is the terraced gardens below it. These were conceived and built between 1550 and 1572 by Cardinal d'Este. The numerous fountains, both large and small, rely on natural water pressure, which takes advantage of the steep slope on which the gardens are built. Water comes mainly from the River Aniene, which was partly diverted through the town. For a long time in the 18th and 19th Centuries the gardens were allowed to fall into a state of decay, but they were taken over by the Italian Government at the beginning of WW1 and have gradually been restored to something close to their original splendor. The gardens were said to have drawn their inspiration from Villa Adriana and, probably, quite a few of the statues used were stolen from there too. In turn, many were stolen from Villa d'Este when it fell into neglect.
Country retreat of the Emperor Hadrian and about equal in area to the old city of Pompeii, today one of Tivoli's World Heritage Sites. Located down the hill back towards Rome (you drive close to it on the Via Tiburtina). It is a very large estate (the largest Roman Villa known) with ruins in various levels of preservation. Entry is €10 for adults. The map given to you for the tour is not very useful. There are audio guides for €4 which require you deposit a ID with them (watch out they have been known to lose them). There are 20 or so pretty long audio snippets for some key places in the estate but each site also has a large sign which also has the same as the audio in text in four languages. Car parking is to the left as you approach the villa and at the entrance area there is a restaurant, a cafe and bookshop too.
Located at the foot of the Roman acropolis in Tivoli, Villa Gregoriana was named after Pope Gregory XVI (1831-1846), who officially commissioned it in 1835. It is situated in a gorge of the waterfalls of the ''Aniene''.