There were no springs with drinking water on the peninsula, during the time of Byzantium it was necessary to build numerous water reservoirs. The largest of them on the entire planet is an underground palace. This place is also called Yerebatan Sarnici.

The underground cistern, kinsterne in Greek, was called a basilica because it was located under the great public square on the first hill of Constantinople, the Basilica of the Stoa.

In this place, even before the construction of the cistern, stood a large basilica, built between 3. the 3rd and 4th centuries during the ancient Roman era as a commercial, legal, and art center. The basilica was reconstructed by Illus after a fire in 476.

Ancient texts indicated that the basilica had gardens, surrounded by a colonnade and facing the important Hagia Sofia mosque. According to them, Emperor Constantine built the structure, which was later rebuilt and enlarged by Emperor Justinian after the Nika riots in 532, which devastated the city.

Historical texts claim that 7,000 slaves participated in the construction of the cistern.

The enlarged cistern provided a water filtration system for the Great Palace of Constantinople and other buildings on the First Hill and supplied water to the Topkapi Palace after the Ottoman conquest in 1453 until modern times.

This cathedral-sized cistern is an underground chamber measuring approximately 138 meters by 65 meters, approximately 9,800 square meters, and capable of holding 80,000 cubic meters of water. The ceiling is supported by 336 mm marble columns, each 9 meters high, arranged in 12 rows of 28 columns, each 5 meters apart.

Most of the columns are predominantly Ionic and Corinthian in style, except for a few Doric styles without carvings. One of the pillars is engraved with images of a hen’s eye, sloping shoulders, and tears. This column resembles the columns of the triumphal arch of Theodosius I from the 4th century (379-395 AD), 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’s cistern.

Most of the columns in the cistern appear to have been recycled from the ruins of older buildings and were probably brought to Constantinople from different parts of the empire, along with those used in the construction of the Hagia Sophia. They are carved and engraved from different types of marble and granite.

52 stone steps lead to the entrance of the cistern to a stunning underground space partially filled with water, in which vaults and colonnades are beautifully mirrored. Two of the 336 columns stand on the heads of the ancient Medusa. The tank is surrounded by a 4-meter-thick burnt brick wall and covered with waterproofing mortar.

The weight of the cistern rests on the columns with the help of cross vaults and circular arches of its roof.

The water was led 971 meters by the Valens aqueduct from the Belgrade Forest to the cistern so that the Great Palace would have a water supply.

The cistern was used as a location for the 1963 James Bond film From Russia with Love. In the film, it is said to have been built by Emperor Constantine, with no reference to Justinian, and is under the Soviet Consulate. Its real location is quite far from the former Soviet Consulate, which is in Beyoğlu, the “newer” European part of Istanbul, on the other side of the Golden Horn.

Concerts are held here in the summer, and the Basilica of the Cistern is a place to rest and cool down on hot summer days.