"Built 135-139 CE on right bank of Tiber River at Ponte Sant'Angelo; originally mausoleum of Hadrian and Antonines; converted to fortress in the 5th century; site of Pope Gregory the Great's vision of archangel Michael in 590; refuge for popes in Middle Ages; made a papal residence in the 14th century; a prison until 1901; the main drum has a diameter of 64 meters and a height of 21 meters."
--http://www.getty.edu/vow/TGNFullDisplay?find=castel+sant%27+angelo&place...
Keywords: Italy, Roma, Rome, Castel Sant' Angelo, San Angelo, fortification, Aurelian Wall, views, ceremonial and/or religious structures, and fortifications. Submitted by Amanda Schlechty for INT STDS 697: Study Abroad. Italy Trip.