In Assassin's Creed Brotherhood, Rome is the setting for most of Ezio's missions.
After the events of Assassin's Creed II, Ezio travels to Rome to confront the Borgia family and rebuild the local Assassin Brotherhood. The city is divided into districts controlled by the Borgia, and Ezio weakens that control by destroying towers, liberating areas, recruiting Assassins, and removing key Templar allies.
Rome serves as both a story setting and a large gameplay system. Ezio can restore shops, landmarks, and services, which improves the city's economy and changes the appearance of districts. The campaign also includes the Vatican and the Colosseum, while the countryside outside Rome hosts additional activities.
Florence and Venice are important to Ezio's earlier adventures in Assassin's Creed II, so they are common mix-ups. Constantinople becomes the main setting of Assassin's Creed Revelations, a later game. Brotherhood's defining city is Rome, even though some missions briefly take place elsewhere.