Castel Sant'Angelo

No building in Rome has lived more lives. Hadrian built it as his mausoleum in 139 AD — a marble-clad drum topped with a garden and a golden quadriga. Aurelian folded it into the city walls as a fortress. Medieval popes turned it into their castle, connected to the Vatican by the Passetto di Borgo, the elevated escape corridor that Clement VII ran along in 1527 while the Sack of Rome burned below him. It has been a prison (Benvenuto Cellini and Giordano Bruno both sat in its cells), an execution ground, a barracks, and since 1901 a museum. Puccini's Tosca leaps to her death from its ramparts — the terrace you finish the visit on.

The route spirals up through all of it: the original Roman burial chamber at the core, reached by Hadrian's own helical ramp; the papal apartments with their surprisingly lavish Renaissance frescoes (Paul III's bathroom is a jewel box); the armoury; the prison cells; and finally the terrace under the bronze archangel Michael — sheathing his sword, as the plague-ending vision of 590 AD had it, which gave the castle its name.

The terrace view is the argument for the ticket: the only high vantage point that has St Peter's dome, the Tiber bridges, and the whole centro storico in one sweep, without the Vatican dome's climb or crowds. Late afternoon light is best; in summer the castle runs evening openings that end with the city lit below.

Cross Ponte Sant'Angelo on the way in — Bernini's angels line the ancient bridge, each holding an instrument of the Passion, and the castle-plus-bridge ensemble from the opposite bank at blue hour is one of Rome's definitive photographs. Queues are modest by Roman standards; it's the low-stress big sight, ideal for a first-day or last-day slot.