The Basilica Cistern which is the largest of several hundred ancient cisterns that lie beneath the city of Istanbul, is located between Haghia Sophia and Coğaloğlu on the historical peninsula of Sarayburnu, was built in the 6th century during the reign of Byzantine Emperor Justinian I. The cistern which contains water today was constructed to provide the water need of the city. Because İstanbul was being besieged by lots of strong civilizations in history, Byzantine Emperors constructed a lot of cisterns to supply the need of water during sieges. Basilica Cistern was reconstructed by Ilius after a fire in 476. The water of the cistern was transported from Belgrade Forest by Cebeci Aqueduct. The cistern, which rendered service in Ottoman Empire era, is very large as its length is 140 meters, width is 70 meters and height is 8 meters.
It means approximately 80.000 cubic meters water. There are 336 columns to hold the ceiling which are constructed with intervals of 4 meters and 12 rows. There are two closed cisterns which are important in İstanbul, Binbirdirek Cistern which is located under the kinder garden between Sultanahmet and Çemberlitaş, and Jesus Cistern which is located in Acımusluk Street near the Big Post Office. Both of them are used as warehouses today.
The enlarged cistern provided a water filtration system continued to provide water to the Topkapi Palace after the Ottoman conquest in 1453 and into modern times. This cathedral-size cistern is an underground chamber approximately 138 meters (453 ft.) by 64.6 meters (212 ft.) – about 9,800 square meters (105,000 sq. ft.) in area – capable of holding 80,000 cubic meters (2,800,000 cu ft.) of water. The ceiling is supported by a forest of 336 marble columns, each 9 meters (30 ft.) high, arranged in 12 rows of 28 columns each spaced 4.9 meters (16 ft.) apart. The capitals of the columns are mainly Ionic and Corinthian styles, with the exception of a few Doric styles with no engravings. One of the columns is engraved with raised pictures of a Hen’s Eye, slanted braches, and tears. This column resembles the columns of the Triumphal Arch of Theodosius I from the 4th century (AD 379-395), erected in the ‘Forum Tauri’ Square. Ancient texts suggest that the tears on the column pay tribute to the hundreds of slaves who died during the construction of the Basilica Cistern. During the big restoration in 1984, ground cleaning was done and original block floor and 2 medusa heads with marble blocks are revealed. It is possible to walk in the cistern with constructed road.