Villa Gregoriana, run by the FAI heritage trust, fills the wooded gorge directly below the old acropolis of Tivoli. A network of stone-paved paths winds down through laurel and ilex woods to a series of waterfalls — including the spectacular Grande Cascata, where the diverted Aniene river plunges 120 metres from a tunnel mouth into the gorge.
It is a steep, sometimes slippery walk, with grottoes, classical ruins, and viewpoints over the falls at every turn. The full circuit takes about two hours and ends at the Temple of Vesta on the opposite rim — making a natural sequel rather than a competitor to a visit to the Villa d'Este.