Hagia Sophia Church located in the intersection of Ataturk Street and Kılıcaslan Street in the center of Iznik is a structure with a basilica plan built in the 4th century. It is the church were 7th Ecumenical Council, which is important for Christians, was held in October 11, 787 during Iconoclasm period (726-843).
After the Ottomans conquered Iznik, it was converted to a mosque in 1331. It had a fire in later years and repaired by Mimar Sinan in request of Sultan Suleiman the Magnificent.
Floor mosaics in the entrance of partially repaired church are enclosed in glass case for protection. Today, Hagia Sophia of Iznik is in the status of memorial museum.