Hagia Sophia or The Church of Holy Wisdom is universally acknowledged as one of the great buildings of the world. This former Byzantine church and former Ottoman mosque in now a museum and its interior reflects both the iconography of Orthodox Christianity and Islam.
Churches had existed on the site since the 4th Century but had been destroyed in war and insurrection Hagia Sophia was rebuilt in her present form between 532 and 537 under the personal supervision of the Emperor Justinian I.
Justinian's basilica was both the culminating of architectural achievement of Late Antiquity and the first masterpiece of Byzantine architecture. Its influence, both architecturally and liturgically, was widespread and can be found in the Eastern Orthodox, Roman Catholic, and Muslim world.
In 1204 the cathedral was attacked by Crusaders en route for the Holy Land and this marked the split between the Eastern Orthodox and Roman Catholic churches. The treasures of Hagia Sofia were carried off to St Mark's in Rome.
The fall of Constantinople in 1453 saw the cathedral turned into an Imperial Mosque and with Christian murals and iconography plastered over it would remain a working mosque for many centuries. Restoration work was undertaken in the mid 19th Century and in 1934 the President Kemal Ataturk ordered that it be turned into a museum. The orthodox murals were exposed. Over the years the building suffered from neglect and decay, but in 1993 following a visit by a UNESCO Mission work began on its repair and restoration.
Further reading and images visit: Hagia Sophia