Built by Justinian in the 6th century, (although there is some evidence that Constantine indeed had a basilica of some sort erected on the site in the 4th century), this building has remained - and rightly so - one of the most magnificent buildings of the world. Destroyed by fire in 404, restored by Theodosius II in 414 and again burnt in the Nika riots of 532, during the reign of Justinian, rebuilt as a major undertaking yet again by him, the dome collapsed and had to be restructured in a slightly different format; conquered eventually by Mehmet II when the Byzantine Empire finally came to a close in 1453 it was turned into a mosque, by him and the minarets added. It remained a mosque for the next 450 years until the birth of the modern state of Turkey and in 1935, under Atatürk, it finally became the museum it is today; a "living" museum of days and glories past; an architectural monument of unique value.