One of the magnificent historical structures of Istanbul is the Basilica Cistern located southwest of Hagia Sophia. Built by the Byzantine Emperor Justinianus I (527-565), this large underground cistern was popularly known as the “Basilica Palace” due to the seemingly countless marble columns rising from the water. Since there was a Basilica on the site of the cistern before, it is also known as the Basilica Cistern.

The cistern is a giant structure covering a rectangular area of ​​140 meters in length and 70 meters in width. There are 336 columns, each 9 meters high, inside this cistern, which is accessed by a 52-step stone staircase. These columns, erected 4.80 meters apart, form 12 rows, each containing 28 columns. The ceiling space of the cistern is transferred to the columns by means of arches. The majority of the columns, which are understood to have been collected from older structures and carved from various types of marble, consist of one piece, while some consist of two pieces. The capitals of these columns have different characteristics in some places. While 98 of them reflect the Corinthian style, some reflect the Doric style. The 4.80-meter-thick brick walls and the brick-paved floor of the cistern were plastered with a thick layer of Khorasan mortar to make them water-proof. Covering a total area of ​​9,800 m2, this cistern has a water storage capacity of approximately 100,000 tons.

Located in the northwest corner of the cistern, the bases of two columns reuse blocks carved with the visage of Medusa. The origin of the two heads is unknown, though it is thought that the heads were brought to the cistern after being removed from a building of the late Roman period. There is no written evidence that suggests they were used as column pedestals previously. Tradition has it that the blocks are oriented sideways and inverted in order to negate the power of the Gorgons’ gaze.

Except for a few that are angular or grooved, the vast majority of the columns in the cistern are cylindrical. The two Medusa Heads used as pedestals under the two columns in the northwest corner of the cistern are masterpieces of Roman sculpture. It is not known from which structures the Medusa heads, which attract the most attention of people visiting the cistern, were taken and brought here. Researchers generally believe that they were brought to the cistern during its construction solely for the purpose of using it as a column base. Despite this view, there are a number of legends about the Medusa Head.

This mysterious place, which is an indispensable part of Istanbul tour programs, has been visited by many people, from former US President Bill Clinton to Dutch Prime Minister Wim Kok, former Italian Foreign Minister Lamberto Dini to former Swedish Prime Minister Göran Persson and former Austrian Prime Minister Thomas Klestil.