Hagia Sophia, or Shrine of the Holy Wisdom of God, was built in 537 AD under the direction of Byzantine Emperor Justinian I, and with the exception of 1204-1261, served as an Eastern Orthodox basilica up until the fall of Constantinople in 1453, when the new Ottoman ruler turned it into a mosque. It was later secularized and opened as a museum in 1935. Although the exterior is a sight to behold, it's the jaw-dropping view of the massive dome from the inside that demands your undivided attention. The building is one of the greatest surviving examples of Byzantine architecture, and held the title of largest cathedral in the world for nearly a thousand years - until the completion of Seville Cathedral in the early 16th century.
See All Things to do in Hagia Sophia »