This cathedral-sized cistern is an underground chamber approximately 143 metres (470 ft) by 65 metres (210 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 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.
The cistern is surrounded by a firebrick wall with a thickness of 4 metres (13 ft) and coated with a waterproofing mortar. The cistern's water was provided from the Belgrade Woods—which lie 19 kilometres (12 mi) north of the city—via aqueducts built by the Emperor Justinian.
Cracks to masonry and damaged columns were repaired in 1968, with additional restoration in 1985 by the Istanbul Metropolitan Museum; the cistern was opened to the public on 9 September 1987.