CASTEL SANT’ANGELO: MAUSOLEUM AND IMPREGNABLE FORTRESS Hadrian's Mausoleum had the shape of a large circular Tower and since the 5th century AD it was transformed into a fortress. This also happened with other Mausoleums such as that of Cecilia Metella on the Appian Way, which was included in the fortification called Castrum Caetani... To read the full article you must log in or register. Login or register