Tivoli is situated along the Aniene river and on the slopes of some high hills nearby the city of Rome. Since ancient times, the town has been taken advantage both for its climates and its strategic position. The natural environment and richness of water has been used over the centuries, for the constructions of large architectural complexes. The most remarkable examples are Villa Adriana, the largest residence ever owned by a Roman emperor; Villa d'Este, with its countless highly entertaining fountains adorning the splendid garden; and Villa Gregoriana, built in the chasm of the Aniene valley, just underneath the acropolis of Tivoli. Villa Adriana and Villa d'Este are both included in the UNESCO World Heritage List. Villa Gregoriana is parte of FAI, the Italian National Trust.