The Great Mosque of the Citadel (Ulu Camii), also known as the Mosque of the Virgin Mary, is the oldest surviving congregational mosque on the mound. It occupies the site of a seventh-century church converted under Abbasid rule and was rebuilt in 1237 CE in Seljuk architectural style. It also features a seventeenth-century Ottoman madrasa in its courtyard and has reopened for regular prayers and services following structural stabilization. For more: Kirkuk Citadel