Tivoli has been a popular summer resort since the days of the Roman Republic. Built as a private summer retreat between AD 118 and 134, Hadrian’s Villa was a vast open-air museum of the finest architecture of the Roman world. The grounds of the Imperial palace covered an area of 300 acres (120 hectares) and were filled with full-scale reproductions of the emperor’s favourite buildings from Greece and Egypt. Among the most impressive buildings we list the Maritime Theater, a small architecture on an island in the middle of a pool – probably Hadrian’ s private studio and the replica of the Canopus, a sanctuary of the god Serapis near Alexandria. Below ground, the emperor built many underground tunnels which linked the various parts of the villa. After the plundering by barbarians in the 6th and 8th centuries, excavations began here in the 16th century. The Villa d’Este was built in the 16th century by Pirro Ligorio for Cardinal Ippolito d’Este. The Villa’s fame rests above all on the terraced gardens and fountains laid out by Ligorio and Giacomo della Porta. The numerous grottoes and fountains still give a vivid impression of the great luxury which the prince of the church enjoyed. Inside the villa there are beautiful manneristic frescoes.