The Roman city where Assassin's Creed: Brotherhood is mainly set is Rome.
The game continues Ezio Auditore's story after Assassin's Creed II. Much of the action takes place in Renaissance Rome, where the Borgia family and their allies hold political and military power. Ezio works to weaken their influence and rebuild the local Assassin Brotherhood.
Rome functions as both a story setting and a large territory that players gradually restore. Reclaiming districts, renovating shops, and recruiting Assassins changes the city and expands the player's resources.
Brotherhood also introduced a major multiplayer mode and developed the series' recruit system. It is not primarily set in Florence or Venice, although both cities are strongly associated with Ezio's earlier adventures in Assassin's Creed II.