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The Basilica Cistern (Turkish: Yerebatan Sarayı - "Sunken Palace", or Yerebatan Sarnıcı - "Sunken Cistern"), is the largest of several hundred ancient cisterns that lie beneath the city of Istanbul (formerly Constantinople), Turkey. The cistern, located 500 feet (150 m) southwest of the Hagia Sophia on the historical peninsula of Sarayburnu, was built in the 6th century during the reign of Byzantine Emperor Justinian I.
The name of this subterranean structure derives from a large public square on the First Hill of Constantinople, the Stoa Basilica, beneath which it was originally constructed. Before being converted to a cistern, a great Basilica stood in its place, built between the 3rd and 4th centuries during the Early Roman Age as a commercial, legal and artistic centre. The basilica was reconstructed by Illus after a fire in 476.
Ancient texts indicated that the basilica contained gardens, surrounded by a colonnade and facing the Hagia Sophia. According to ancient historians, Emperor Constantine built a structure that was later rebuilt and enlarged by Emperor Justinian after the Nika riots of 532, which devastated the city.
Historical texts claim that 7,000 slaves were involved 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 continued to provide water to the Topkapi Palace after the Ottoman conquest in 1453 and into modern times.
Measurements and data 
This cathedral-size cistern is an underground chamber approximately 138 metres (453 ft) by 64.6 metres (212 ft) - about 9,800 square metres (105,000 sq ft) in area - capable of holding 80,000 cubic metres (2,800,000 cu ft) of water. The ceiling is supported by a forest of 336 marble columns, each 9 metres (30 ft) high, arranged in 12 rows of 28 columns each spaced 4.9 metres (16 ft) apart. The capitals of the columns are mainly Ionic and Corinthian styles, with the exception of a few Doric style 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. The majority of the columns in the cistern appear to have been recycled from the ruins of older buildings (a process called 'spoliation'), likely brought to Constantinople from various parts of the empire, together with those that were used in the construction of Hagia Sophia. They are carved and engraved out of various types of marble and granite.
Fifty-two stone steps descend into the entrance of the cistern. The cistern is surrounded by a firebrick wall with a thickness of 4 metres (13 ft) and coated with a waterproofing mortar. The Basilica Cistern's water came from the Eğrikapı Water Distribution Center in the Belgrade Forest, which lie 19 kilometres (12 mi) north of the city. It traveled through the 971 metres (3,186 ft)-long Valens (Bozdoğan) Aqueduct, and the 115.45 metres (378.8 ft)-long Mağlova Aqueduct, which was built by the Emperor Justinian.
The cistern has the capacity to store 100,000 tons of water, despite being virtually empty today with only a few feet of water lining the bottom.
The weight of the cistern lies on the columns by means of the cross-shaped vaults and round arches of its roof.
The Basilica Cistern has undergone several restorations since its foundation. The first of the repairs were carried out twice during the Ottoman State in the 18th century during the reign of Ahmed III in 1723 by the architect Muhammad Agha of Kayseri. The second major repair was completed during the 19th century during the reign of Sultan Abdulhamid II (1876–1909). Cracks to masonry and damaged columns were repaired in 1968, with additional restoration in 1985 by the Istanbul Metropolitan Museum. During the 1985 restoration, 50,000 tons of mud were removed from the cisterns, and a platforms built throughout to replace the boats once used to tour the cistern. The cistern was opened to the public in its current condition on 9 September 1987. In May 1994, the cistern underwent additional cleaning.
Medusa column bases 
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, however it is widely thought that one was placed sideways only to be the proper size to support the column. The upside down Medusa was placed that way specifically because she would be the same height right side up.
In media 
The cistern was used as a location for the 1963 James Bond film From Russia with Love. In the film, it is referred to as being constructed by the Emperor Constantine, with no reference to Justinian. Its location is a considerable distance from the Soviet (now Russian) consulate, which is located in Beyoğlu, the "newer" European section of Istanbul, on the other side of the Golden Horn.
The finale of the 2009 film The International takes place in a fantasy amalgam of the Old City, depicting the Basilica Cistern as lying beneath the Sultan Ahmed Mosque, which, in the film, is directly adjacent to the Süleymaniye Mosque.
In the 2011 video game, Assassin's Creed: Revelations, the player controlled character, Ezio Auditore, is given the chance to explore a section of this cistern in a memory sequence entitled The Yerebatan Cistern.
The cistern with its inverted Medusa pillar was used prominently in the climax of Inferno: The Novel by Dan Brown featuring Robert Langdon, where antagonist planned to make his attack.
See also 
- Media related to Basilica Cistern of Constantinople at Wikimedia Commons
- Basilica Cistern of Istanbul - Thewotme travelblog
- Byzantium 1200 | Basilica Cistern
- A Photo Essay About The Basilica Cistern