Hagia Sophia is a former Greek Orthodox Christian patriarchal cathedral, later an Ottoman imperial mosque and now a museum in Istanbul, Turkey. It was constructed in 537 AD and served as an Eastern Orthodox cathedral until 1453. After the Ottoman conquest of Constantinople in 1453, it was converted into a mosque. In 1935, it was converted into a museum by the Republic of Turkey. The building is famous for its massive dome, which was the largest in the world for nearly a thousand years.
