Ortaköy Mosque (Turkish: Ortaköy Camii) or  'Great Mosque of Sultan Abdulmejid') in Beşiktaş, Istanbul, Turkey, is a mosque situated at the waterside of the Ortaköy pier square, one of the most popular locations on the Bosphorus. It was commissioned by the Ottoman sultan Abdülmecid I and its construction was completed around 1854 or 1856.ts architects were Armenian father and son Garabet Balyan and Nikoğos Balyan, who worked as a team and who also designed the nearby Dolmabahçe Palace and the Dolmabahçe Mosque in 1853–1855