Hagia Sophia

Hagia Sophia, officially the Hagia Sophia Grand Mosque (Turkish: Ayasofya-i Kebir Cami-i Şerifi), is a mosque and major cultural and historical site in Istanbul, Turkey. Originally a Greek Orthodox church, the site has changed between being a mosque and a museum since the fall of the Byzantine Empire.

Originally built by the eastern Roman emperor Justinian I as the Christian cathedral of Constantinople for the state church of the Roman Empire between 532 and 537, and designed by the Greek geometers Isidore of Miletus and Anthemius of Tralles, it was formally called the Church of the Holy Wisdom and was then the world's largest interior space and among the first to employ a fully pendentive dome. It is considered the epitome of Byzantine architecture and is said to have "changed the history of architecture". The present Justinianic building was the third church of the same name to occupy the site, as the prior one had been destroyed in the Nika riots. As the episcopal see of the ecumenical patriarch of Constantinople, it remained the world's largest cathedral for nearly a thousand years, until Seville Cathedral was completed in 1520. Beginning with subsequent Byzantine architecture, Hagia Sophia became the paradigmatic Orthodox church form, and its architectural style was emulated by Ottoman mosques a thousand years later. It has been described as "holding a unique position in the Christian world" and as an architectural and cultural icon of Byzantine and Eastern Orthodox civilization.

The religious and spiritual centre of the Eastern Orthodox Church for nearly one thousand years, the church was dedicated to the Holy Wisdom. It was where the excommunication of Patriarch Michael I Cerularius was officially delivered by Humbert of Silva Candida, the envoy of Pope Leo IX in 1054, an act considered the start of the East–West Schism. In 1204, it was converted during the Fourth Crusade into a Catholic cathedral under the Latin Empire, before being returned to the Eastern Orthodox Church upon the restoration of the Byzantine Empire in 1261. The doge of Venice who led the Fourth Crusade and the 1204 Sack of Constantinople, Enrico Dandolo, was buried in the church.