Villa Gregoriana in Tivoli is a complex of wooded parks, paths, waterfalls, grottoes and vegetation extending to the foot of the ancient acropolis a suggestive natural park immersed in greenery and situated near Rome. Commissioned by Pope Gregory XVI in around 1834, this splendid unspoiled place was a must for artists and nobility alike, who came to the ancient city of Tibur on their grand tour in the nineteenth century. The whole area of the villa is under the protection and management of the Fondo Ambiente Italiano or FAI (the Italian Environmental Fund) and is considered unique in the world a place where nature and human work merge amid the extraordinary beauty of the landscape, precious marbles and archaeological remains of the ancient villa of Publius Manlius Vopisco. Villa Gregoriana is world famous both for its Great Waterfall, a much photographed scenic fall created by the River Aniene, and for the Grottoes of Neptune or Grottoes of the Sirens, river-eroded caves situated under the area of the Temple of Vesta and that can be reached through a tree-lined avenue adorned with flowers and vines. Near the extraordinary villa is the Gregorian Bridge, a fascinating structure also commissioned by Pope Gregory XVI and which today connects the park to Tivoli's old town centre. The bridge offers a wonderful view of the Aniene valley and of the ancient acropolis.