Justinian I commissioned Hagia Sophia’s present building in Constantinople, completed in 537.
The current structure replaced an earlier church destroyed during the Nika riots of 532. Emperor Justinian ordered a much grander rebuilding and appointed the mathematician Anthemius of Tralles and the geometer Isidore of Miletus as its principal designers. The church was dedicated in 537, although later earthquakes led to repairs and alterations.
For nearly a thousand years, Hagia Sophia served as the cathedral of Constantinople and the principal church of the Byzantine Empire. After the Ottoman conquest of the city in 1453, it became a mosque. In 1935 it opened as a museum, and in 2020 it was reconverted into a mosque.
Hagia Sophia is often called a cathedral because of its original Christian role, but its religious status has changed over time. Its massive dome and pendentives made it a landmark in the history of architecture.