Parks and nature reserves Parco di Villa Gregoriana Villa Gregoriana is a beautiful nature park in the city of Tivoli. It was set up in 1834, at the behest of Pope Gregory XVI, after the River Aniene diverted thus bringing the arrangement of a new waterfall. The structure is dominated by two temples located in the acropolis and consists of different natural elements, panoramic views and caves that make it the most visited park in the city.