Morning
The Vatican Museums demand your freshest hours — book the earliest slot you can. Pace yourself through the Raphael Rooms so you arrive at the Sistine Chapel with attention to spare. Afterwards, St Peter's Basilica: the dome climb (several hundred steps) buys you the definitive view over Bernini's colonnaded square and the whole city beyond.
Afternoon
Lunch nearby at Pizzarium, Gabriele Bonci's celebrated pizza al taglio counter near the Cipro metro stop — order by weight, eat standing. Then follow the river to Castel Sant'Angelo and cross the angel-lined bridge in front of it, one of Rome's great photographs. Metro or walk to the Spanish Steps, then browse your way down Via dei Condotti toward the Corso.
Evening
Spend your last hours in Monti, the village-like quarter between the Forum and Termini: aperitivo in Piazza della Madonna dei Monti, dinner at whichever enoteca has a free table, and a final unhurried look at the floodlit Colosseum, five minutes downhill — the city insists on ending where it began.
Tip: Skip the gelato shops with fluorescent, mounded tubs near the big monuments. Walk two streets in any direction to an artisan gelateria — muted colours and covered tins are the reliable tells — and order the pistachio as the benchmark.
Two days in Rome is an argument for a third. But done this way, it is a complete story: empire in the morning, God at noon, dinner with the Romans at night.