Castel Sant'Angelo

Castel Sant'Angelo is a cylindrical fortress on the right bank of the Tiber in Rome, built between 123 and 139 AD as a mausoleum for the emperor Hadrian and his family. Its original form was a towering rotunda crowned with a garden and a gilded quadriga, and it briefly stood as the tallest building in Rome. Around 401 AD the structure was folded into the city's defenses as a military fortress and incorporated into the Aurelian Walls, and from the fourteenth century popes converted it into a castle and refuge, linking it to St. Peter's Basilica by the covered corridor known as the Passetto di Borgo. The building was decommissioned as a military and papal stronghold in 1901. It now operates as the Museo Nazionale di Castel Sant'Angelo, drawing more than 1.2 million visitors a year.