Tivoli is famous for its splendid vistas from the Parco Garibaldi in the center of town (view Rome and the Mediterranean on clear days) and from the nearby Villa D'Este, which is Tivoli's best known ornament. The D'Este villa is built on the foundations of one of the first-century Roman estates. The Roman building had first been rebuilt as a Benedictine convent, which, in turn, became the governor's mansion. What we see today is what Cardinal Ippolito D'Este (the son of Lucrezia Borgia and Alfonso I, Duke of Ferrara ) made of the structure after becoming governor in 1550. Ippolito also had his architect clear away the part of town downhill from the villa to construct the vast terraced garden and divert part of the flow of the Aniene to provide water for the garden's 500 great and small fountains. It passed into Austrian hands by bequest in the 19th century, and, from 1865 until his death in 1886, it was the home of Franz Liszt. Italy regained the estate after World War I. Work on restoration of the building and gardens proceeded slowly until the mid-1990s, when a major effort was made to complete the work in time for the 2000 Jubilee Year. The D'Este villa and gardens are now in the best condition that they have seen in several hundred years.
Work at the Villa Adriano, the villa that Hadrian built in the early 2nd century below the town, was also completed in 2000. New walkways make the ruins much more accessible, and fences around pits and along exposed raised areas have made the site much safer -- although the fences do take some of the adventure out of visiting the site. Hadrian's villa was neglected -- almost forgotten -- for more than 1000 years until Flavio Biondo, the 15th century founder of the science of archeology and of Christian and medieval topography, mentioned it in his in his encyclopedias, which were the foundation for all subsequent dictionaries of Roman archeology and antiquities. Piranesi made drawings of the Villa Adriana in the 18th century while the first modern archeological digs at the site were in progress. The Government of Italy bought the site from the Braschi family after the fall of the Papal States in 1870. The site is currently in very good condition. Some statues, which have long been displayed in Museums in Rome, have been replaced with good concrete replicas, and the site museum, which had been closed for years, was completely redone and reopened in 2000.
Villa D'Este -- Piranesi's drawing: http://special.lib.gla.ac.uk/images/exhibitions/treasures/az24_33.jpg
D'Este villa and gardens: http://sgwww.epfl.ch/berger/Jardin-noframe/tivoli-intro_english.html
Villa Adriana (Hadrian's Villa): http://sights.seindal.dk/sight/901_Hadrians_Villa.html,