In Assassin's Creed Revelations, Ezio Auditore's main base is Constantinople.
Ezio travels to Constantinople, the capital of the Byzantine Empire, while searching for Altaïr Ibn-La'Ahad's Masyaf keys. The game is set in the early sixteenth century, when the city is also widely known by its later name, Istanbul.
Constantinople provides the game's principal open-world environment, including districts on both sides of the Golden Horn. Ezio works with the local Assassin faction and becomes involved in the political struggle surrounding Sultan Bayezid II and his sons.
Rome is Ezio's main base in Assassin's Creed: Brotherhood, while Florence and Venice are especially important locations in Assassin's Creed II. Those settings belong to different stages of Ezio's life.