Rome is the historical city that contains the Colosseum in Assassin’s Creed Brotherhood.
Brotherhood is set primarily in Rome during the early 16th century. Ezio Auditore works there to weaken the Borgia family’s power and rebuild the Assassin Brotherhood, while the city serves as the game’s large central environment.
The Colosseum is one of Rome’s most recognizable landmarks and appears alongside locations such as the Pantheon, the Vatican, Castel Sant’Angelo, and the Roman Forum. The game combines historically recognizable architecture with fictionalized missions and characters.
Florence and Venice are especially associated with Assassin’s Creed II, while Constantinople is the main setting of Revelations. Those cities also belong to Ezio’s broader storyline, which is why they are sometimes mixed up with Brotherhood’s Rome campaign.