The Church of the Holy Wisdom, known as Hagia Sophia in Greek, is a former Byzantine church and former Ottoman mosque in Istanbul. It is one of the greatest surviving examples of Byzantine architecture, rich with mosaics and marble pillars and coverings. Hagia Sophia was rebuilt in her present form between 532 and 537 under the personal supervision of Emperor Justinian I. Justinian's basilica was both the culminating architectural achievement of Late Antiquity and the first masterpiece of Byzantine architecture. Its influence, both architecturally and liturgically, was widespread and enduring in the Eastern Orthodox, Roman Catholic, and Muslim worlds alike. Unfortunately, to this day nothing remains of the original Hagia Sophia, which was built on this site in the fourth century by Constantine the Great. Constantine, himself among other emperors was the fisrt Christian emperor known in history. The Hagia Sophia was one of several great churches he built in important cities throughout his empire. The architects of the church were Isidore of Miletus and Anthemius of Tralles, who were professors of geometry at the University of Constantinople. Their work was a technical triumph, even though the structure was severely damaged several times by earthquakes. The original dome collapsed several times, as it was rebuilt after 558 but it collapsed again in 563. Despite this violent setback, Hagia Sophia remained a functioning church until May 29, 1453, when Sultan Mehmet the Conqueror entered triumphantly into the city of Constantinople. He was amazed at the beauty of the Hagia Sophia that he took it upon himself and immediately converted it into his imperial mosque. All interior surfaces are sheathed with polychrome marble, green and white with purple porphyry, and gold mosaics.