Aya Sophia was first constructed as a Church and then became a Mosque under the Muslim rulers of Turkey. http://en.wikipedia.org/wiki/Hagia_Sophia. Now it is a museum with a curious mixture of Christianity and Islam. Our visit to the Aya Sophia was very short and hurried. One requires more time to take in the differences between that and the Blue Mosque even since my memories are already getting mixed up! Actually, I could have easily spent another whole week in Istanbul and still not have had enough time to take in the sights! All the pictures of Christ and other Christian symbols were painted over when the Cathedral was converted to a Mosque. The Islamic things like the mihrab http://en.wikipedia.org/wiki/Mihrab and minbar http://en.wikipedia.org/wiki/Minbar were added during the Ottoman reign. The large dome was typical of the Byzantine architecture.