Mausoleum of Hadrian
Castel Sant'Angelo is one of the most historic places in Rome, overlooking the course of the Tiber. In 135 AD, the emperor Hadrian decided to build a large funeral monument for his family. But in the following century, the emperor Aurelian transformed the building into a fortress, playing a key role in the control of the city. At the end of the 14th century, the castle became the property of the Church State and was connected to the Vatican by a section of the walls called the Passetto. In case of danger, it also becomes a refuge for the popes.