Justinian I ordered the construction of Hagia Sophia in Constantinople.
The present Hagia Sophia was built under the Byzantine emperor Justinian I after the previous church was destroyed during the Nika riots of 532. Construction began that same year, and the new building was dedicated in 537.
Architects Anthemius of Tralles and Isidore of Miletus designed the structure. Its vast central dome, carried by pendentives, was an engineering achievement that influenced Byzantine and later Ottoman architecture.
Hagia Sophia served as the principal cathedral of Constantinople for centuries. After the Ottoman conquest of the city in 1453, it became a mosque. It was converted into a museum in 1935 and reconverted into a mosque in 2020, while remaining a major historic monument open to visitors.