Particularly striking is the awesome sight of the partially ruined Colosseum in the distance at the end of a wide, traffic-choked road; the glorious Trevi Fountain tucked away in a square dotted with souvenir shops; and St Peter's and the Vatican set snootily aloof across the river in a country all of their own.
Rome is a vast city, but the centre is actually quite small, considering how many layers of history are packed within it - Etruscan tombs sit alongside Republican meeting rooms, Imperial temples overlook early Christian churches and mediaeval bell towers, Renaissance palaces and baroque basilicas all share the same piazza.