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Cisterns of Byzantine Constantinople 

While Constantinople is famous for its strategic location, the triangular peninsula on which the city rested lacked sufficient fresh water sources. A large number of cisterns supplied by aqueducts were built in Late Antiquity to help supply water to the growing population of Constantinople. These cisterns include huge open cisterns or reservoirs, like the Cistern of Aetius, as well as covered or underground cisterns, like the Basilica Cistern. They are among the most impressive Byzantine structures of modern Istanbul.

Constantinople’s insufficient water sources made cisterns an essential feature of its water supply system. The city had to rely on its Thracian hinterland for water, as the city itself had no rivers, a few small springs and a long dry summer with little rainfall. The Lycus (Lykos), while often called a river, was in fact a small stream emptying into a bay that was later transformed into the Harbor of Theodosius. There were also a few natural springs that later became associated with the Virgin Mary, such as the famous holy spring (hagiasma) at the Church of Blachernai. As none of these water sources provided adequate water for city’s growing population in Late Antiquity (which perhaps was half a million in the 5th-6th century), Constantinople came to acquire an unprecedented number of cisterns. Recent research has documented more than 200 cisterns from the Byzantine era in the city, with most of them being covered cisterns built prior the 7th century. They became central to Constantinople’s water supply system and required significant maintenance. Major cisterns were usually placed on or near the top of hills to supply water to various buildings, such as public baths, palaces, monasteries, and churches. These cisterns stored the water brought in by aqueducts, as there were water shortages during the long dry summers of the region. They were also essential for the security of the city, particularly during sieges.

An incredible number of covered cisterns were built in Constantinople, including the largest and most famous underground cistern known as the Basilica Cistern. This cistern was built during the reign of Justinian I (527-565), probably during the reconstruction of the Basilica Stoa above it, which was finished in 541. It is around 138 x 65 meters and is supported by 336 columns. The second largest covered cistern is the so-called “Cistern of Philoxenos”, which measures 64 x 56 meters with 224 columns. A short distance east is one of the oldest covered cisterns - the so-called “Theodosius Cistern”, which is around 24x40 meters and has 32 columns. The first recorded covered cistern was the Cistern of Modestus, which was completed in 369. While it did not survive, it was probably the cistern used for the Ottoman Saddler’s Market known as Saraçhane. It was measured at 154 x 90 meters.

Several large open-air water reservoirs were built at high points of the city following the construction of the Theodosian Walls. The plan of the open cisterns is rectangular or square, with masonry of alternating bands of ashlar and brick. Two of these open cisterns, the Cistern of Aetius and the Cistern of Aspar, were located on the Valens line between the Constantinian and Theodosian walls. It is possible that the open cistern were used for commercial and agricultural purposes rather than for public use. The Cistern of Aetius (244 x 85 m) was probably built in 421 when Aetius served as the eparch of Constantinople. The Cistern of Aspar (152 square meters) was built in 459 by the Patrician Aspar, an influential 5th century figure of Alan descent who served as magister militum and consul. The Cistern of St. Mocius (170 x 147 meters) seems to date to the reign of Anastasius (491–518). Perhaps around the 6th or 7th century, another open cistern was constructed in the suburb of Hebdomon, and perhaps supplied the army camp and imperial palace located here. In addition, there is a massive wall in Cağaloğlu that seems to be the remains of another open cistern. 

Cisterns were supplied by a gravity-based system that brought water from the hinterland of the city. It seems to have consisted of Hadrian’s line, which entered the city just north of Kaligaria Gate (Eğri Kapı), passed near the cistern near the Pantokrator Monastery and ended at the Basilica Cistern. It also supplied the area around the Great Palace, the Baths of Zeuxippus and the Hippodrome. The Valens line probably entered the city north of Gate of Charisius (Edirnekapı), supplied the open cisterns of Aetius and Aspar, crossed the Aqueduct of Valens and terminated in the Cistern of Philoxenos. The water supply of Constantinople decreased in the 7th and 8th century as the Avars cut the Valens line during the Siege of Constantinople of 626, and was only restored around 765 by Constantine V (741-775). It is unclear how seriously damaged the Valens line was, which could have had disastrous implications for the city’s demographics. While it has generally been argued that the Valens line ceased functioning completely, it also has been suggested that the city continued to be supplied by water sources closer to the city. 

The next recorded work on the water system dates to the reign of Basil II (976-1025). Large amounts of water were required in this period, as the city possibly reached around half a million by the 11th century. Repairs were also made on the aqueducts around 1170 during the reign of Manuel I Komnenos (1043-1080). It seems that the long-distance water system was beyond repair by the 12th century, so the city possibly mostly relied on the water sources from the Belgrade Forest, as it did later during the Ottoman era. The water supply system was not repaired following the Latin conquest of Constantinople in 1204, after which cisterns became the main source of water in the city. While large cisterns required a functioning aqueduct system to supply water, it is possible that some of the smaller cisterns primarily collected rainwater through the Byzantine era. Collecting rainwater became much more important after the aqueduct lines were no longer functioning. This is likely true at many of the cisterns at monasteries, like the cisterns under Pammakaristos and Chora. It is possible that rainwater was channeled to these cisterns from the monasteries’ rooftops.

Cisterns are a possible source of a wide range of information about Byzantine Constantinople. In the Early Byzantine era, most of the large covered cisterns were built around the oldest area of the city, on the First and Second Hill near the Great Palace and the Hippodrome. The size of these cisterns seems to reflect the density and location of the population at the time. During the Middle Byzantine era, a large number of cisterns were built on the northern slopes of the Fourth and Fifth Hills of the city, which perhaps indicates that the population density was higher here during this period. There were also a significant number of cisterns around the First Hill during this period. It also seems that some cisterns also help mark the location of certain streets, as seems to be the case of the cisterns on Sofular Street.

Many cisterns were located within the enclosure of the monasteries, as seen in the cluster of cisterns around the Pantokrator Monastery. Some substructures and crypts were converted into cisterns, particularly in the Middle and Late Byzantine eras. The cistern under the naos of the Pammakaristos Monastery, for example, was possible a crypt belong to an older structure – later converted into a cistern. Many older building, including the Sphendone of the Hippodrome, the Palace of Lausus, and the Myrelaion rotunda, were eventually converted into cisterns as well. The open cisterns cease to function after 1204 and by the Ottoman era, they were used as gardens (known in Turkish as çukurbostan or “sunken garden”).  The Byzantine cisterns of the city were not used for the supply or distribution of water during the Ottoman era. However they were often used for other purposes. For example, many of the surviving covered cisterns were later used in the production of silk during the Ottoman era.


Most of the covered cisterns had a rectangular or square plan. They typically had vaults supported rows of marble or granite columns, brick and mortar walls, brick tiles or stone floors. The walls were lined with hydraulic plaster (opus signinum) while the corners typically were beveled to decrease pressure against the corners. The remains of staircases have also been found in some of the cisterns. The height of hydraulic mortar, along with calcium deposits on the walls, gives an idea of the water level of the cisterns, which in some cases seems to have reached the springing of the arches. Cisterns in Constantinople frequently used columns rather piers commonly used by the Romans to reduce maintenance costs. Wooden beams were placed between the springing of arches to reinforce the structure. Reused capitals were also common in the cisterns of Constantinople. The most striking example is the Gorgon capitals in the Basilica Cistern, which used as pedestals. There are other unique capitals, though the most common is the Ionic impost capital. Impost blocks also made an early appearance in cisterns. The majority of the capitals are made of Proconnesian marble between the fourth and sixth centuries showing at least some degree of damage. The marble quarries at the island of Proconnesus ceased production in the 7th century, after which the use of materials from stock or reused materials from older structures became more widespread. These factors make it more difficult to date the cisterns.

Gorgon capital at Basilica Cistern

Mason’s Mark at the Cistern of Philoxenos

Corinthian capital with crosses on impost and column at Sultan Cistern

Capitals at Myrelaion Rotunda Cistern

Capital from Bible House Cistern

From the Nicholas V. Artamonoff Collection


Capital in Ipek Bodrum Cistern by William Earl Betsch

From Dumbarton Oaks


Basilica Cistern by W.H. Bartlett (1838)

Description of the Basilica Cistern from De Aedificiis by Procopius

I shall now describe the labours which were carried out here by this Emperor to ensure an abundant water-supply. In the summer season the imperial city used to suffer from scarcity of water as a general thing, though at the other seasons it enjoyed a sufficiency.  Because that period always brings droughts, the springs, running less freely than at the other seasons, used to deliver through the conduits a less abundant flow of water to the city.  Wherefore the Emperor devised the following plan. At the Imperial Portico, where the lawyers and prosecutors prepare their cases, as well as all others who are concerned with such matters, there is a certain very large court (aulê), very long, and broad in proportion, surrounded by columns (peristylos) on the four sides (tetrapleuron), not set upon a foundation of earth by those who constructed it, but built upon living rock. Four colonnaded stoas surround the court, standing one on each side. Excavating to a great depth this court and one of the stoas (that which faces toward the south), the Emperor Justinian made a suitable storage reservoir for the summer season, to contain the water which had been wasted because of its very abundance during the other seasons. For receiving this overflow of the aqueduct  when its stream is spilling over, this cistern both furnishes a place for the water which for the moment can find no space, and provides a supply for those who need it when water becomes scarce. Thus the Emperor Justinian made provision that the people of Byzantium should not be in want of fresh water.

Drawing by W.H. Bartlett (1838).jpg

Basilica Cistern by Thomas Allom (1836)

Cistern of Philoxenos by Thomas Allom (1836)

Mark Twain’s description of the cistern from The Innocents Abroad (1869):

“We visited the Thousand and One Columns. I do not know what it was originally intended for, but they said it was built for a reservoir. It is situated in the centre of Constantinople. You go down a flight of stone steps in the middle of a barren place, and there you are. You are forty feet under ground, and in the midst of a perfect wilderness of tall, slender, granite columns, of Byzantine architecture. Stand where you would, or change your position as often as you pleased, you were always a centre from which radiated a dozen long archways and colonnades that lost themselves in distance and the sombre twilight of the place.”

Cistern of Philoxenos by W.H. Bartlett (1838)

Cistern of Philoxenos by Guillaume Berggren (1870)


Cistern of Philoxenos by Sebah & Joaillier

The Water Supply of Byzantine Constantinople by Crow, Bardill, & Bayliss

İstanbul'da Bizans Dönemi Sarnıçlarının Mimari Özellikleri ve Kentin Tarihsel Topografyasındaki Dağılımı by Kerim Altuğ

Two Romes: Rome and Constantinople in Late Antiquity edited by Lucy Grig and Gavin Kelly

​Bildlexikon zur Topographie Istanbuls: Byzantion, Konstantinupolis, Istanbul by Wolfgang Müller-Wiener

The Longest Roman Water Supply Line by Kâzım Çeçen

İstanbul'da Bizans Dönemi Sarnıçlarının Mimari Özellikleri ve Kentin Tarihsel Topografyasındaki Dağılımı by Kerim Altuğ

Die Byzantinischen Wasserbehalter von Konstantinopel by Forchheimer & Strzygowski

​“Tarihi Yarımada'da Bizans Dönemi Sarnıçları Envanteri Işığında Topografik Gözlemler” by Kerim Altuğ

“The Byzantine Cisterns of Constantinople” by K. A. Ward, M. Crapper, K. Altuğ and J. Crow

“The infrastructure of a Great City: Earth, Walls and Water in Late antique Constantinople” by James Crow

“The water supply of Constantinople: Archaeology and Hydrogeology of an Early Medieval City” by P. Bono, J. Crow, and R. Bayliss

“The Water Supply of Constantinople” by Cyril Mango

Oxford Dictionary of Byzantium edited by Alexander Kazhdan


De Aedificiis (Buildings) by Procopius (translated by H.B. Dewing)

The Innocents Abroad by Mark Twain


Byzantine Cisterns of Constantinople Photo Album (Byzantine Legacy Flickr)

Water Supply (Nicholas V. Artamonoff Collection)

William Earl Betsch Photographs of Architectural Capitals in Istanbul (Dumbarton Oaks)

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