The Basilica Cistern is located in the eastern part of Constantinople, opposite the church of Hagia Sophia.
It is a roofed cistern with a capacity of 78.000 m3. It was constructed by Justinian (527-565) below the Basileios Stoa, which was destroyed during the Nika riots (532). It has 336 columns (28 columns arranged in 12 rows), many of which support Corinthian capitals, spolia from older buildings. The bases of two columns on the southwest side of the monument bear the carved face of Medusa, work originating from past years.
The Basilica Cistern supplied with water the Great Palace of Constantinople, the Patriarchal Complex and other residences in the area. Because of its size, it has been called by the Turks Yerebatan Saray (sunken palace).
The cistern was abandoned through the course of the years when it was re-discovered in 1545 by Petrus Gyllius, French historian and natural scientist, who visited Constantinople in the years 1544-1547. Later, the cistern was used for the irrigation of the Topkapi gardens.
The monument has been repaired in the years of Ahmed III (1703-1730) and Abdulhamid II (1876-1909). After its restoration in 1985-1987, it is now open to the public.