The Colosseum is in almost every pass
The Colosseum with the Roman Forum and the Palatine is included outright in the City Pass, the Essentials Pass and the Rome Tourist Card. In the Roma Pass, the 72-hour OMNIA Card and the Explorer Pass it is one of the entries you choose. The 24-hour OMNIA tier does not reach it at all. Whichever route you take, the time slot is compulsory, so see the Colosseum ticket page before you plan the day.
The Vatican Museums split the field
The Vatican Museums with the Sistine Chapel are included in both Turbopass passes and in both OMNIA tiers, and they are a pick in the Explorer Pass. In the Tourist Card they are one half of a choice, the other being the Pantheon. The Roma Pass does not cover them: the Vatican is a separate state, and the city pass stops at its border. That single line decides many trips, and the Vatican ticket page covers the alternative.
Castel Sant'Angelo, Pantheon and the bus
Castel Sant'Angelo belongs to the City Pass and is a choice in the Roma Pass, the 72-hour OMNIA Card and the Explorer Pass. The Pantheon, which has charged entry since 2023, sits in both Turbopass passes and is a pick in the Explorer Pass and one half of the Tourist Card choice. The hop-on hop-off bus comes as 48 hours of Big Bus with a Tiber boat in the City Pass, as the open bus in both OMNIA tiers, whose Colosseo stop is suspended, and as one Big Bus day among the Explorer Pass picks. Ostia Antica is included in the City Pass and is a choice in the Roma Pass, the OMNIA Card and the Explorer Pass.
What no pass includes
The dome climb at St Peter's is in none of the six. The Borghese Gallery and the Capitoline Museums appear only in the passes that work by choice, never in the two Turbopass packages. Public transport is part of the Roma Pass and the 72-hour OMNIA Card, an add-on with the City Pass and absent everywhere else, with Fiumicino excluded throughout. More on the public transport page.
Reservation rules
The Colosseum admits visitors in timed slots and on named tickets, pass or not. The City Pass and the Essentials Pass reserve the Colosseum and Vatican slots at purchase. The Roma Pass leaves the Colosseum booking to you and excludes the arena and the underground. The OMNIA Card reserves each sight through the link on the voucher, the Explorer Pass through its own app after activation, and the Tourist Card fixes every slot at booking. The Borghese Gallery has to be reserved weeks ahead in all cases.