In Assassin's Creed Revelations, Ezio explores the memories of Altaïr Ibn-La'Ahad in Constantinople.
Ezio travels to Constantinople in the early sixteenth century to find keys connected with Altaïr's former headquarters at Masyaf. Using the Animus, he experiences Altaïr's memories at several points in the older Assassin's life, including events after the first game.
The two storylines are linked by the Masyaf keys and by the series' recurring theme of knowledge passed across generations. Ezio is not simply replaying the original game's campaign: Revelations presents later chapters of Altaïr's life and shows how he reshaped the Levantine Brotherhood.
Constantinople, called Istanbul in some modern contexts, is Ezio's principal historical setting in Revelations. The game's modern-day sections continue Desmond's arc, but the central historical pairing is Ezio's search and Altaïr's memories.