Constantinople is Ezio's main base of operations in Assassin's Creed Revelations.
The game takes Ezio Auditore to the Ottoman capital, where he searches for keys connected to Altaïr Ibn-La'Ahad's legacy. Constantinople, known today as Istanbul, is divided into districts that Ezio explores while working with local Assassins and opposing Byzantine Templars. The city's location between Europe and Asia makes it a fitting meeting point for the game's overlapping historical storylines.
Revelations also alternates between Ezio's Renaissance-era missions and scenes from Altaïr's life in Masyaf. The narrative therefore serves as a direct bridge between the two protagonists. Ottoman prince Suleiman appears as a young historical figure during the events of the game.
Constantinople is not the same setting as Alexandria in Assassin's Creed Origins or Athens in Assassin's Creed Odyssey. Those cities belong to different periods and protagonists, while Revelations focuses on Ezio's final major adventure.