The main historical setting of Assassin's Creed Revelations is Constantinople.
The game is set in the early sixteenth century, primarily in Constantinople, the capital of the Byzantine and later Ottoman worlds. Ezio Auditore travels there to recover keys connected with Altaïr Ibn-La'Ahad's library in Masyaf and becomes involved in the city's political and factional struggles.
The city is presented through districts on both sides of the Golden Horn, including areas such as Galata and the Imperial District. Ottoman Sultan Bayezid II and his sons are among the historical figures connected to the story, while the fictional Assassin conflict supplies the main plot.
Constantinople was officially renamed Istanbul in the twentieth century, long after the game's period. That is why “Istanbul” is a common modern reference but not the historical name emphasized by the game's setting. The title also includes playable sequences in Masyaf and Cappadocia, but Constantinople is its principal city.