Which city contains the historic Hagia Sophia landmark?

Istanbul contains the historic Hagia Sophia landmark.

Hagia Sophia stands in Istanbul’s Old City, overlooking the Golden Horn and the Bosporus. The present building was completed in 537 under Byzantine Emperor Justinian I and served for centuries as the cathedral of Constantinople, the capital of the Byzantine Empire.

After the Ottoman conquest of Constantinople in 1453, Hagia Sophia became an imperial mosque. In 1935 it opened as a museum under the Turkish Republic, and in 2020 it was reconverted into a mosque. The building is famous for its enormous dome, mosaics, marble decoration, and layered Christian and Islamic history. Istanbul was known as Constantinople for much of its medieval and early modern history, but the modern city officially adopted the name Istanbul in the 20th century.