Constantinople is the primary setting for Ezio's final major adventure in Assassin's Creed: Revelations.
The game takes Ezio to the Ottoman capital in the early 16th century, where he searches for keys connected to Altaïr's legacy. Constantinople, called Istanbul today, is divided into districts that Ezio explores through climbing, investigation, combat, and stealth. The city gives the game a setting distinct from the Italian locations of the earlier Ezio stories.
Ezio encounters Ottoman figures including Prince Suleiman, who later became Sultan Suleiman the Magnificent. The narrative also returns to Masyaf and includes playable sequences featuring Altaïr Ibn-La'Ahad, linking the two Assassin protagonists.
Rome is the main city of Brotherhood, while Florence and Venice are prominent in Assassin's Creed II. Alexandria is associated with Origins. Those locations belong to other entries, making Constantinople the specific answer for Revelations' central setting.