Castel Sant'Angelo

Castel Sant’Angelo began its life in the 2nd century AD as the mausoleum of Emperor Hadrian, built between 123 and 139 AD to house his remains and those of the Antonine emperors.
By the 5th century, the mausoleum was transformed into a fortress and incorporated into Rome’s defensive walls to protect the city and the nearby Vatican area 
Its name, “Castel Sant’Angelo,” comes from a legend: during a plague in 590 AD, Pope Gregory I saw a vision of the Archangel Michael sheathing his sword atop the building, signaling the end of the epidemic.
After centuries of military and papal use, the castle eventually became a museum in 1901, preserving nearly two thousand years of Roman history within its walls.