Castel Sant'Angelo began life in 139 AD as Emperor Hadrian's mausoleum, a towering drum of cement over 150 feet high. Its spiral ramp once carried imperial funeral processions five storeys up to deposit emperors' ashes in the Room of Urns, where trap doors and murder holes protected the dead from intruders.

The castle's longest-serving executioner, Giovanni Battista Bugatti, spent 68 years beheading over 500 men here, though between appointments he sold umbrellas to tourists. Among its more colourful prisoners was Benvenuto Cellini, a goldsmith who enjoyed satanic ceremonies in the Colosseum and stabbing his girlfriend's lovers.

Six different statues of the Archangel Michael have crowned the fortress over the centuries, the first made of wood until it weathered away. Puccini set the final act of Tosca here, where the heroine throws herself from the ramparts.

VoiceMap's self-guided tours trace the castle's transformation from imperial tomb to papal fortress, revealing how its 58 rooms became a labyrinth of prison cells, Renaissance apartments and a centrally heated bathroom with marble tub, explaining the building's reinvention through plague, siege and Medici excess.