Hagia Sophia’s original cathedral was completed in 537 under Byzantine Emperor Justinian I.
The building in Istanbul was the third major church constructed on the site. The previous church was destroyed during the Nika riots of 532, after which Justinian commissioned a much larger replacement. Architects Anthemius of Tralles and Isidore of Miletus designed the new structure, whose vast dome became a landmark of Byzantine engineering.
Hagia Sophia served as the cathedral of Constantinople for centuries. After the Ottoman conquest of the city in 1453, it became a mosque, and minarets and other Islamic architectural features were added. In 1935, the Turkish Republic converted it into a museum. It was reconverted into a mosque in 2020.
The building’s name means “Holy Wisdom,” not the name of a saint named Sophia. Its history reflects the changing religious and political identity of Constantinople, later called Istanbul.