The Flavian Amphitheatre opened in AD 80 and held about 50,000 spectators. Book a timed Colosseum ticket in advance — the same ticket usually covers the Roman Forum and Palatine Hill later on this route. Metro Line B to Colosseo drops you at the door. Closed 25 December and 1 January; hours shift with sunset. Walk this order. Outer arches and the Arch of Constantine view → arena floor → hypogeum if your ticket includes it → upper tier for the Forum and Palatine skyline.

Hadrian’s mausoleum became a papal fortress, then a museum. From the ramparts you look straight down the Passetto and across the Tiber to the dome. St Peter’s Square and Basilica sit a short walk west in Vatican City. Get there. Walk Ponte Sant’Angelo (Bernini’s angels) to the castle. Continue along Via della Conciliazione to the Square, or take bus 40/64 / Metro A Ottaviano–San Pietro if legs are done. Book and dress. Castle tickets are timed. The Basilica is free, with airport-style security. Shoulders and knees covered. Dome climb is a separate ticket and a lot of steps. Walk this order. Ponte Sant’Angelo → castle courtyard and ramp → Raphael rooms / loggia if open → terrace view of the dome → Via della Conciliazione → St Peter’s Square colonnade → Basilica nave, baldachin and apse → dome only if you still have the energy.