Hagia Sofia, Istanbul

The last of three church buildings was completed in 537 AD. The site was an Eastern Orthodox church from 360 AD to 1204, when it was converted to a Catholic church following the Fourth Crusade.

It was reclaimed in 1261 and remained Eastern Orthodox until the Ottoman conquest of Constantinople in 1453. It served as a mosque until 1935, when it became a museum. In 2020, the site once again became a mosque.