Hagia Sophia, located in Istanbul, Turkey, and now known as the Ayasofya Museum, was the greatest Christian cathedral of the Middle Ages. It was later converted into an imperial mosque in 1453 by the Ottoman Empire, and further into a museum in 1935. For centuries, it stood at the heart of two of the world's great religions. To Christians, it was Hagia Sophia, Church of the Holy Wisdom, mother church of the Orthodox faith and of the old Byzantine Empire. To Muslims, it became Ayasofya Camii, Mosque of Holy Wisdom and the Jewel of Istanbul. And for people of all faiths, it was a spectacle of marvellous beauty.