"The rather forbidding round form of Castel Sant’Angelo dominates many views of the River Tiber. Conceived by Hadrian (AD117-138) as his mausoleum, it has been remodelled over the years and has served as a mausoleum for a number of other emperors and their families, a papal refuge, prison, garrison for Napoleonic troops, and now as a museum. The castle is constructed on four main floors with the beautiful papal apartments on the upper two storeys. It is crowned by a huge bronze statue of the Archangel Michael, which has given the castle its name." (P. Harcourt Davies, Fiona Nichols: Rome and the Vatican, 2006).