In Assassin's Creed: Revelations, Ezio investigates Altaïr's legacy in Istanbul, historically known during the game's period as Constantinople.
The game takes place mainly in the Ottoman capital in the early sixteenth century. Ezio travels there to find five Masyaf Keys, which open the vault containing knowledge left by Altaïr Ibn-La'Ahad. The city provides districts, markets, underground passages, and landmarks for the game's exploration and missions.
The wording can cause confusion because the game and many historical references use Constantinople, while the modern English name of the city is Istanbul. Constantinople was the common historical name in the period depicted, and the city was also known as Kostantiniyye in Ottoman usage. Istanbul became the official name of the Turkish state’s largest city in the twentieth century.
Revelations connects three timelines: Ezio's Ottoman-era journey, Altaïr's final years, and Desmond's modern-day experience. That structure makes the city a bridge between the franchise's major Assassin protagonists.