Rome has a reputation for requiring elaborate planning. For a weekend it requires exactly two bookings, and the rest can be decided over coffee each morning.
The two bookings
The Colosseum, timed slot, one to two weeks ahead. The ticket includes the Roman Forum and Palatine Hill and is valid across two days — better value than most visitors realise.
The Vatican Museums, two to four weeks ahead, earliest slot available.
That is the list. If you also want the Borghese Gallery, it needs a booked two-hour slot — and it is the best museum experience in Rome precisely because of that cap.
Do not combine them
The Vatican and the Colosseum are on opposite sides of the city, each needs three hours minimum, and both involve queues.
Splitting them across two days is what makes a Rome weekend work rather than exhaust.
Day one: ancient
Colosseum at opening. Then the Forum — take an audio guide or app, because it is a field of fragments with minimal signage and almost nothing explains itself.
Walk northwest: Piazza Venezia, the Pantheon, Piazza Navona, Campo de' Fiori.
Evening in Trastevere across the river.
Day two: papal, then free
Vatican Museums on the earliest slot. Three hours, ending at the Sistine Chapel.
St Peter's Basilica is a separate site, free, with its own security queue — many visitors assume one ticket covers both. The dome climb is extra and worth it.
Afternoon: the churches, which is what short-trip visitors miss.
San Luigi dei Francesi — three Caravaggios in one chapel. Santa Maria del Popolo — two more. San Pietro in Vincoli — Michelangelo's Moses.
All free, all usually without a queue, and better than most ticketed museums.
Finish at the Trevi Fountain late, when it is merely busy rather than impassable.
Leave for a longer trip
Ostia Antica, forty minutes away and nearly as complete as Pompeii.
Tivoli, and the Baths of Caracalla.
The Appian Way by bicycle.
All excellent, all a half day or more.
Practical
Shoes. Twelve to fifteen kilometres a day on sampietrini cobbles worn smooth.
Water. Around 2,500 nasoni street fountains run continuously with cold water. Block the spout with a finger and it jets from a hole on top.
Dress code at St Peter's and the Vatican Museums — shoulders and knees covered, enforced, for men too.
Coffee standing at the bar: €1.20. Seated on a piazza: €4–6. Both posted.
Fiumicino is 32 minutes by express train. Ciampino is coach or bus and slower.