It is also known as the Basilica Cistern because it is located under the Stoa Basilica.Cistern is a giant structure that covers an area of 140 meters in length and 70 meters in rectangular form. There are 336 columns, each 9 meters high, inside the cistern, which is descended by a 52-step stone staircase. These columns, erected at intervals of 4.80 meters from each other, form 28 rows of 12 in each row.
After the conquest of Istanbul by the Ottomans in 1453, it was used for a while and water was supplied to the gardens of Topkapı Palace, where the sultans lived. The cistern, which is understood not to have been used by the Ottomans who preferred fountain water instead of stagnant water after establishing their water facilities in the city, was rediscovered by Dutch traveler Petrus Gyllius who came to Istanbul in 1544-1550 to investigate byzantine ruins.
Also, according to legend, Medusa is one of three Gorgons in Greek mythology that are the female monsters of the underworld. Of these three sisters, snake-headed Medusa has the power to turn those who look at her into stone. According to one view, gorgon paintings and sculptures were used to protect large structures and special places at that time, and that is why the head of Medusa was placed on the cistern.