This ancient structure offers exceptional city views and boasts an incredible history, having protected some of the city’s most influential people. Construction here began in 135 under the direction of Emperor Hadrian, who wanted to use it as a mausoleum. In 1277 an 800-metre fortified corridor connected the castle to the Vatican City so the Pope could escape if he was in danger and, during the 1527 sieges, Pope Clement VII used the fortress as a refuge. Today the castle boasts five floors showcasing frescoes from the Renaissance period.