One of the magnificent ancient buildings of İstanbul is the Basilica Cistern located in the southwest of Hagia Sofia. Constructed for Justinianus I, the Byzantium Emperor (527-565), this big underground water reservoir is called as “Yerebatan Cistern” among the public because of the underground marble columns. As there used to be a basilica in the place of the cistern, it is also called Basilica Cistern.
