In the very heart of Istanbul, a two-minute walk from the majestic Hagia Sophia, beneath the noisy streets of the Sultanahmet district, lies one of the most astonishing and atmospheric structures of the Byzantine Empire — the Basilica Cistern. Locals call it Yerebatan Sarnıcı, which means "Sunken Palace." And this name perfectly conveys the impression that everyone descending underground experiences: you find yourself not in an engineering structure, but in a true underground palace with high vaults, mysterious semi-darkness, and endless rows of columns receding into the depths.
The Basilica Cistern is an ancient underground reservoir built to supply water to the Great Imperial Palace of Constantinople and its adjacent buildings. Today, it is one of the largest and best-preserved monuments of the Byzantine era, over one and a half thousand years old.
Construction History: From Constantine to Justinian
The history of the Basilica Cistern began long before its final construction. The construction of the reservoir was started during the reign of Emperor Constantine I the Great at the beginning of the 4th century, when he was transferring the capital of the Roman Empire to the shores of the Bosphorus. However, the grand project was only completed by Emperor Justinian I the Great in 532 AD — the same year he began rebuilding Hagia Sophia after the devastating Nika Revolt.
The emperors of Constantinople created their city to be majestic, luxurious, and rich. This idea extended even to utilitarian structures: the underground reservoir was built not as a simple water tank, but as a real palace or a huge temple. Hence its name — the Basilica Cistern. The word "cistern" translates from Greek as "reservoir," and "basilica" means "temple" or "royal hall." The name is also related to the fact that the reservoir was located beneath a vast public square — the Stoa Basilica, one of the city`s main squares.
An Engineering Marvel of the 6th Century
The dimensions of the Cistern are impressive even today. The length of the underground structure is 145 meters, the width is 65 meters, and the area reaches almost 9,800 square meters. The reservoir`s capacity is 80,000 cubic meters of water, comparable to the volume of 30 Olympic swimming pools.
The vaulted ceiling of the cistern is supported by 336 marble columns, each 8–9 meters high. They are arranged in 12 rows of 28 columns, spaced 4.8 meters apart, creating a true underground forest. The walls, 4 meters thick, are made of fire-resistant brick and coated with a special waterproofing mortar — the hydraulic engineering technologies of the 6th century amaze even modern engineers with their sophistication.
Water was supplied to the cistern via a system of aqueducts, the main one being the famous Aqueduct of Valens, from springs in the Belgrade Forest, located about 19 kilometers north of the city. This was a grand engineering project that provided the empire`s capital with water in case of drought or prolonged siege.
The Secret of the Basilica Cistern`s Columns: Where Did They Come From?
One of the most interesting questions that arises for every visitor is: where did all these columns come from and why are they so different? The answer is simple and astonishing at the same time: the vast majority of the columns were brought from ancient temples and earlier Roman structures. In architecture, this phenomenon is called "spolia" — the reuse of architectural elements from old buildings in new constructions.
In the Late Antique period, when the cistern was built, this was common practice. Emperors not only saved resources but also deliberately used elements of ancient structures to emphasize the continuity of power and the grandeur of the empire. Columns were brought to Constantinople from all corners of the vast empire — from Greece, Asia Minor, Egypt, and Italy itself.
This is why the columns in the Basilica Cistern vary so much. Here you can see columns made of different types of marble — white, pinkish, gray, veined and plain. They differ in their method of finishing, their capitals, and their height. Some columns consist of a single solid piece of stone, while others are assembled from two parts. Among the capitals, Ionic and Corinthian styles predominate, but Doric ones without ornamentation are also found.
One column is particularly notable: carved on it are images that researchers call the "Hen`s Eye," the "Slanted Branches," and the "Tears." This column resembles the columns of the Triumphal Arch of Theodosius I, erected in the 4th century on the Forum Tauri square. Ancient texts suggest that the image of tears on the column is a tribute to the memory of the hundreds of slaves who perished during the construction of the cistern.
The Medusa Head: The Main Enigma of the Cistern
The most famous attraction of the Basilica Cistern is two columns at the base of which rest the heads of the Gorgon Medusa. One head is placed upside down, the other is turned sideways.
The origin of these heads and their exact purpose remain a subject of debate among researchers. It is known that they were brought from some more ancient structure, presumably from a temple dedicated to Medusa. A similar head is kept in the courtyard of the Istanbul Archaeological Museum, confirming the theory that these artifacts originate from the same architectural complex.
Why are the heads positioned so strangely? There are several versions. According to ancient Greek mythology, Medusa the Gorgon was a monster with snakes for hair, whose gaze turned all living things to stone. Therefore, the builders may have deliberately turned the heads upside down and sideways to neutralize the magical power so that no one would fear turning to stone upon accidentally meeting her gaze. Another, more prosaic version is that the heads were simply used as convenient bases for the columns, and the strange positioning is explained by the need to fit them to the required height.
Be that as it may, these enigmatic heads have become the true symbol of the Basilica Cistern and attract thousands of tourists eager to touch the mystery of millennia.
Obscurity and Rebirth of the Basilica Cistern
After the Ottoman conquest of Constantinople in 1453, the cistern continued to be used for some time — water from it was supplied to Topkapi Palace. However, over time, with the advent of more modern water supply systems, the reservoir became unnecessary and was abandoned.
The cistern was practically forgotten for several centuries. It was rediscovered completely by accident. In 1545, the Dutch traveler and antiquities researcher Petrus Gyllius, while studying Byzantine antiquities in Istanbul, became intrigued by the fact that local residents were getting water from holes in their basements and even fishing there. He began investigating and, to his astonishment, discovered a whole forest of columns underground.
For a long time, the Basilica Cistern remained polluted and largely inaccessible. It was only in 1987, after extensive cleaning and restoration, that it was opened to the public as a museum. In 2022, following another restoration, the cistern once again opened its doors to visitors.
The Basilica Cistern Today: A Journey into the Underground World
Today, the Basilica Cistern is one of Istanbul`s most visited museums. Entering, you descend a staircase several meters underground and find yourself in a completely different world. Here, a semi-darkness, coolness, and an astonishing silence always prevail, seeming incredible after the city`s noisy streets.
There is very little water in the cistern now — about 50 centimeters. But it is still clean and transparent, and fish even swim in it. Wooden walkways are laid out for visitors, allowing you to wander among the columns, examining their capitals, bas-reliefs, and, of course, the famous Medusa heads. The columns are illuminated from below, and the color of the lighting constantly changes, creating an incredibly beautiful and mysterious atmosphere.
In one corner of the Basilica Cistern, there is a "Wishing Pool," at the bottom of which coins tossed by tourists glisten. On a raised platform near the exit, there is a small cafe where you can rest after your walk.
The cistern has repeatedly been used as a film location. The most famous scene is from the James Bond film "From Russia with Love." After that, the cistern began appearing in other films and adventure novels — for example, in Dan Brown`s "Inferno," Umberto Eco`s "Baudolino," and Victor Pelevin`s "The Invincible Sun."
Visitor Information
The Basilica Cistern is located in the Sultanahmet district, opposite Hagia Sophia. It is very easy to find: the entrance is right across the street from Hagia Sophia, near the "Sultanahmet" tram stop.
The museum is open daily. Entrance is paid. The best time to visit is early morning, when there are still few tourists, or in the evening, when the lighting creates a particularly beautiful atmosphere. Queues here can be quite long, so it is advisable to plan your visit in advance.
The Basilica Cistern represents a unique monument where Byzantine engineering met the legacy of antiquity. 336 columns, brought from ancient temples and public buildings, became not just building material but a kind of museum of Roman architecture in the open air — or rather, beneath the vaults of the earth. Ionic and Corinthian capitals, different types of marble, mysterious bas-reliefs — every stone here has its own story, stretching back centuries.
