The Hagia Sophia, otherwise known as the Sancta Sophia or the Church of Holy Wisdom, was a former Eastern-Orthodox Christian basilica located in the Imperial District of Constantinople. Following the fall of the city in 1453 to Ottoman hands, it was converted into an Islamic mosque by Mehmet II, where it was also used as a library.
Designed by the Byzantine Greek scientists Isidore of Miletus and Anthemius of Tralles, Hagia Sophia was completed by the order of the Roman Emperor Justinian at the year 537, where it served as the imperial, patriarchal cathedral. This continued until 1453, where after the fall of Constantinople to the Ottoman forces of Sultan Mehmet II, it was converted into an imperial mosque shortly after.
Half a century later, in the year 1510, the Janissary Murat Bin Husn concealed the armor of Ishak Pasha inside the Hagia Sophia. The following year, Ezio Auditore da Firenze recovered Ishak Pasha's scattered memoirs and entered the mosque, where within minutes, he had climbed to the ceiling of the dome and activated an entrance to the armor's storage room, before taking the set back to the Galata headquarters.
Also in 1511, Sofia Sartor requested some white tulips from Ezio, and, after he tracked a florist to the Hagia Sophia, he learned that he could find some of the flowers in the courtyard. Following this, he also discovered that Sofia had prepared a picnic in the shadow of the great mosque, before he handed the bouquet he had picked with his Hidden Blade over to her.
- The achievement "Spider Assassin" could be earned by climbing the Hagia Sophia from its base to the pinnacle in under 25 seconds.
- One of Ishak Pasha's memoir pages was located on the pinnacle of the landmark.
- The Hagia Sophia was a purchasable landmark in Constantinople, for the price of 60,400 Akçe.
- In reality, Hagia Sophia only had two minarets in 1511. Darby McDevitt explained that the landmark's representation having four minarets "was the iconic image of the Hagia Sofia" and had to be in the game.
- The interior of the Hagia Sophia appeared much larger than the entire structure itself when standing outside the building.