Roman emperor Hadrian’s mausoleum later became Rome’s Castel Sant’Angelo.
Construction began around 135 CE, during Hadrian’s reign, and the monument was completed by his successor Antoninus Pius in 139 CE. The cylindrical tomb stood beside the Tiber and was connected to the city by the Pons Aelius, now commonly called Ponte Sant’Angelo.
The mausoleum originally contained the ashes of Hadrian and several later emperors, including Antoninus Pius, Marcus Aurelius, and Septimius Severus. Its upper structure was probably decorated with statues and crowned by a sculpture of Hadrian driving a quadriga.
The building changed function as Rome’s political and military fortunes shifted. It became a fortress, a papal refuge, and eventually a museum. Its modern name comes from a medieval legend that the archangel Michael appeared above the structure during a plague.