One of the magnificent ancient building 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".
The cistern is 140 meters long and 70 meters wide and covers a rectangular area as a giant structure. Accessible with 52 step staircase, the Cistern shelters 336 columns, each of which is 9 meters high. Erected at 4.80 meters intervals from one another the columns are composed of 12 rows, each has 28 columns. The case-bay of the cistern is conveyed by the columns through arches. Majority of the columns, most of which is understood to have been compiled from the ancient structures and sculpted of various kinds of marbles, is composed of a single part and one of it is composed of two parts. The head of these columns bears different features in parts. 98 of them reflect the Corinthian style and part of them reflect the Dorian style. The cistern has 4.80 meters high brick walls, and the floor is covered by bricks, and plastered by a thick layer of brick dust mortar for water tightness. Covering 9,800 sqm area in total, the cistern has an estimated water storage capacity of 100,000 tons.
The column, known as "Tear of Crying Column", has an appearance as if it were crying because it is wet, unlike other columns. This column resembles the columns of the Triumphal Arch of Theodosius I from the 4th century, erected in the "Forum Tauri" Square. It is reported that the Crying Pillar was built the memory of hundreds of slaves who lost their lives during the construction of the Basilica Cistern.
Except a couple of the edges and grooved columns of the cistern, a majority of them are shaped like a cylinder. Two Medusa heads, which are used as support under the two columns at the northwest edge of the cistern, are the great work of art from the Roman period. What attracts the most attention from the visitors is that the structure from which the Medusa heads have been taken is unknown. The researchers often consider that it has been brought for being used as supports to the column at the time of construction of the cistern. However, this has not prevented myths for the heads of Medusa.
As the legend has it, Medusa is one of the three Gorgons that are female monsters in the underground world in Greek mythology. The snake-head Medusa, one of the three sisters has the power of gorgonizing the ones that happen to look at her. Accordingly, Gorgone paintings and sculptures were being used for protecting big structures and special venues in that time. And putting the head of Medusa in the cistern was for protection purposes. According to another rumor, Medusa was a girl who boasted for her black eyes, long hair and beautiful body. She loved Perseus, the son of Zeus. Athena was also in love with Perseus and this made Medusa jealous. Therefore, Athena converted Medusa's hairs into snakes. Now, everybody that happened to look at Medusa was gorgonized. Afterwards, Perseus headed off Medusa and beat many enemies by using her power.