re: #13 Ojoe

That’s inaccurate, the building was constructed in 532-537. It was already there.

The Hagia Sophia was originally built as a church by Justinian I, but it was converted by the Muslim invaders into a mosque after the fall of the Eastern Roman Empire in 1453. That included removing Christian iconography and the construction of the minarets at the corners of the facility.

The building was turned into a museum in 1935 and it remains one of the best and largest examples of dome on pendentive form in the world; enabling the square form to translate into the circular form above.