Basilica Cistern

The Basilica Cistern, or Cisterna Basilica (Greek: Βασιλική Κινστέρνα, Turkish: Yerebatan Sarnıcı or Yerebatan Sarayı, "Subterranean Cistern" or "Subterranean Palace"), is the largest of several hundred ancient cisterns that lie beneath the city of Istanbul, Turkey. The cistern, located 150 metres (490 ft) 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.^[1] Today it is kept with little water, for public access inside the space.

Basilica Cistern

Greek: Βασιλική Κινστέρνα Turkish: Yerebatan Sarnıcı
Basilica Cistern
Shown within Istanbul Fatih Show map of Istanbul Fatih Basilica Cistern (Turkey) Show map of Turkey
Location	Istanbul
Coordinates	41°0′29″N 28°58′40″E
Site notes
Public access	Yes
Website	www.yerebatan.com

Cisterna Basilica is located to the west of Hagia Sophia and is of a similar size. The square on the left of the map marks the location of the Cistern of Philoxenos.

History

This subterranean cistern was called Basilica because it was located under a large public square, the Stoa Basilica, on the First Hill of Constantinople.^[2] Prior to its construction, a great basilica stood on the spot. It had been built during the Early Roman Age between the 3rd and 4th centuries as a commercial, legal and artistic centre.^[1] The basilica was reconstructed by Illus after a fire in 476.

Ancient texts indicated that the basilica cistern contained gardens surrounded by a colonnade that faced the Hagia Sophia.^[1] According to ancient historians, Emperor Constantine built a structure that was later reconstructed 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.^[1]

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 Topkapı Palace after the Ottoman conquest in 1453 and into modern times.

The existence of the cistern was eventually forgotten by all but the locals who still drew water from it until, in 1565, the French traveller Petrus Gyllius left a record of it. Gyllius recorded being rowed in between the columns and seeing fish swimming in the water beneath the boat.^[3]

Restoration history

1985–1987 works

The first major modern restoration of the Basilica Cistern was undertaken by the Istanbul Metropolitan Municipality between 1985 and 1987.^[4] More than 50,000 tons of silt were removed from the reservoir, uncovering the Medusa-head column bases.^[5] Elevated wooden walkways were introduced, allowing the structure to open to the public as a museum in 1987.^[6]

2020–2022 restoration

A comprehensive restoration was carried out between 2020 and 2022 by the İBB Miras team.^[5] The deteriorated iron tie-rods were replaced with stainless-steel tension rods, anchored with star-shaped plates, to improve seismic resilience.^[7]

Concrete walkways and a 50 cm-thick cement render added in the mid-20th century were dismantled. Approximately 1,440 m³ of concrete and 1,600 m³ of sediment were removed, revealing the original 6th-century Byzantine brick floor beneath.^[5]

A new modular steel walkway was installed, physically separated from the historic structure, improving structural performance and visitor experience.^[5] Conservation treatments included gentle cleaning of marble and brick surfaces to remove biological growth and salt crystallization.^[4]

New LED lighting and sensors were also installed to support atmospheric lighting and non-invasive digital exhibitions.^[5]

Legal status and conservation framework

The Basilica Cistern is part of the "Historic Areas of Istanbul," a UNESCO World Heritage Site since 1985.^[8] Nationally, it is protected under Turkey’s Law No. 2863 on the Conservation of Cultural and Natural Property as a 1st-degree archaeological site.^[9]

This classification restricts permanent alterations and mandates that all interventions be reversible and approved by the Istanbul No. 1 Cultural Heritage Preservation Board.^[9] In 2011, the board ordered the restriction of heavy vehicle traffic near the site to mitigate vibration-related damage.^[4]

Adaptive reuse and exhibitions

In 2022, the Basilica Cistern hosted the digital exhibition Daha Derine ("Going Deeper"), curated by İBB Miras.^[5] The exhibition featured contemporary artworks by Jennifer Steinkamp, Ozan Ünal, Aslı İrhan, and Ali Abayoğlu, using projection mapping, sculpture, and light to reflect on the site’s themes of memory, mythology, and water.

These installations were temporary, non-invasive, and mounted on reversible infrastructure added during the 2020–2022 restoration.^[5]