Beneath the busy streets of Sultanahmet in Istanbul lies a mysterious underground world that has fascinated visitors for centuries. Known as the Basilica Cistern, or Yerebatan Sarnıcı in Turkish, this extraordinary Byzantine structure is one of the most remarkable historical landmarks in the city.
Built in the 6th century during the reign of Emperor Justinian I, the enormous underground reservoir once helped supply water to the imperial buildings of Constantinople. Today, its hundreds of ancient columns, dimly illuminated walkways, mysterious Medusa heads, and unusual architectural details create an atmosphere unlike anywhere else in Istanbul.
But the Basilica Cistern is more than an impressive example of ancient engineering. It is also home to stories that have survived for centuries.
Why are two enormous Medusa heads placed upside down and sideways? Why does one column appear to be crying? Was the cistern really forgotten for hundreds of years? And what secrets are hidden beneath its water?
Here are the most fascinating secrets and legends of Istanbul’s Basilica Cistern.
1. The Mystery of the Upside-Down Medusa Heads
Perhaps the most famous mystery inside the Basilica Cistern is the pair of enormous Medusa heads used as column bases.
Located in the northwestern section of the cistern, one Medusa head is positioned upside down, while the other is placed sideways.
Both sculptures are believed to originate from an earlier Roman structure and were reused during the construction of the cistern.
But why were they placed in such unusual positions?
Several explanations have emerged over the years.
The Mythological Explanation
In Greek mythology, Medusa was one of the Gorgons, a creature whose gaze could turn people into stone. According to the most familiar version of the myth, anyone who looked directly into her eyes would be transformed into a statue.
One popular interpretation suggests that the builders deliberately turned the heads upside down and sideways to neutralise Medusa’s frightening power.
However, there is no historical evidence confirming that this was the builders’ intention.
The Practical Explanation
Another explanation is much simpler. The Medusa sculptures may have been reused as convenient stone blocks to support the columns.
Ancient builders frequently reused architectural materials from older structures, and the Basilica Cistern contains many examples of this practice.
The exact reason for the unusual positioning remains unknown, making the Medusa heads one of the most intriguing features of the cistern.
2. The Weeping Column: Why Does It Look Like It Is Crying?
Another fascinating feature of the Basilica Cistern is the column commonly known as the Weeping Column.
Unlike the other columns, its surface contains unusual carvings resembling tears or eyes. Moisture on the marble makes the markings appear even more striking under the cistern’s atmospheric lighting.
According to local legend, the column represents the tears of workers who lost their lives during the construction of the enormous underground reservoir.
The story suggests that the column was created as a memorial to those who suffered while building the cistern.
Although this is a popular legend, there is no reliable historical evidence confirming that the carvings were intended to commemorate the workers.
An architectural explanation offers another possibility. Similar decorative patterns have been identified on other ancient monuments in Istanbul, suggesting that the column was reused from an earlier Roman structure.
Regardless of its original purpose, the Weeping Column remains one of the most memorable details inside the Basilica Cistern.
3. A Giant Underground Reservoir Built for an Empire
The Basilica Cistern was constructed around 532 AD during the reign of Byzantine Emperor Justinian I.
At that time, Constantinople was one of the most important cities in the world. Its growing population, imperial palaces, religious buildings, and public facilities required a reliable water supply.
The cistern was designed to store water brought into the city through its extensive aqueduct system.
Its scale was extraordinary for its time.
Some of its most impressive architectural features include:
- 336 columns: The enormous underground chamber is supported by 336 marble and granite columns.
- 12 rows: The columns are arranged in twelve rows, with 28 columns in each row.
- Approximately 9 metres high: Each column supports the brick arches and vaulted ceiling.
- Around 9,800 square metres: The cistern covers an enormous underground area.
- Approximately 80,000 cubic metres of capacity: It was designed to store a vast amount of water.
Many of the columns and decorative elements were taken from older Roman buildings and reused.
This explains why the columns have different styles, materials, and decorative capitals. Rather than being designed as a uniform architectural collection, they were assembled from available materials to create a practical and impressive water reservoir.
4. Why Is It Called the Basilica Cistern?
The name Basilica Cistern comes from the ancient public structure known as the Stoa Basilica, which once stood above the site.
The word basilica originally referred to a large public building used for civic, commercial, or administrative purposes in the Roman world.
When the underground reservoir was constructed beneath this earlier complex, it became associated with the name of the structure above it.
In Turkish, the cistern is called Yerebatan Sarnıcı, which can be translated as the Sunken Cistern.
The name is inspired by the enormous underground space and the rows of columns that appear to rise out of the water.
Today, both names are widely used, although Basilica Cistern is the name most commonly recognised by international visitors.
5. The Cistern That Was Forgotten for Centuries
One of the most surprising parts of the Basilica Cistern’s history is that this enormous structure was not always a famous tourist attraction.
After Constantinople was conquered by the Ottomans in 1453, the cistern continued to be used for a period, including supplying water to the gardens of Topkapı Palace.
However, as the city’s water infrastructure developed, its importance gradually declined.
For centuries, the underground reservoir remained largely out of public view.
Interestingly, local residents living above the cistern reportedly continued drawing water through wells and openings in their homes. Some even caught fish from the water below.
The structure was brought to wider attention in the mid-16th century by the French scholar and traveller Petrus Gyllius, also known as Pierre Gilles.
While researching Byzantine remains in Istanbul, he heard reports that residents were obtaining water from underground openings.
After investigating, he discovered the enormous reservoir and documented his experience.
His account helped introduce this remarkable Byzantine structure to a wider European audience.
6. The 50,000 Tonnes of Mud That Hid the Secrets
For many years, the Basilica Cistern was not presented to visitors in the way it is today.
Over time, mud and debris accumulated inside the structure, covering parts of its floor and concealing important architectural details.
A major restoration and cleaning project carried out between 1985 and 1987 transformed the cistern.
During these works, approximately 50,000 tonnes of mud were removed.
The cleaning revealed important features, including the famous Medusa heads, which became internationally recognised symbols of the cistern.
Walkways were also installed, allowing visitors to explore the underground structure safely.
The Basilica Cistern officially opened as a museum in 1987.
A further comprehensive restoration project took place between 2017 and 2022, including structural strengthening and improvements to the visitor experience.
The cistern reopened in July 2022 with a new lighting design and updated visitor facilities.
7. Did the Basilica Cistern Have a Connection to the Great Palace?
Yes. One of the most important purposes of the Basilica Cistern was to provide water for the Great Palace of Constantinople and the surrounding imperial buildings.
The Great Palace was the residence of Byzantine emperors and an enormous complex of buildings, courtyards, halls, and ceremonial spaces.
Much of the palace has disappeared over the centuries, but its remains and archaeological discoveries still help historians understand the scale of the imperial district.
The Basilica Cistern was an essential part of this infrastructure.
Its large storage capacity helped ensure that water remained available even when the city’s external water supply was interrupted.
In a city that experienced sieges, political conflicts, and changing weather conditions, reliable water storage was essential.
The cistern was therefore not simply an architectural wonder. It was an important part of the survival and daily operation of the Byzantine capital.
8. The Secret Behind the Different Columns
Walking through the Basilica Cistern, visitors may notice that not all 336 columns look alike.
Some have elaborate Corinthian capitals, while others have simpler designs. Their materials, proportions, and decorative details also vary.
This is not an architectural mistake.
The differences are largely explained by a practice known as spolia, the reuse of architectural materials from older buildings.
Instead of producing every column from newly quarried stone, Byzantine builders incorporated existing columns and decorative elements from earlier Roman structures.
This approach saved time and resources while allowing valuable materials to be reused.
The result is an unusual collection of columns that reflects different periods of ancient architecture.
In a way, the cistern is also a museum of reused Roman craftsmanship hidden beneath the streets of modern Istanbul.
9. The Mysterious Atmosphere of the Underground World
The Basilica Cistern is often described as one of the most atmospheric historical places in Istanbul.
The combination of shallow water, ancient columns, brick vaults, reflections, and carefully designed lighting creates an extraordinary environment.
The structure was originally built for practical purposes, not as a monument intended to impress visitors.
Yet its scale and architectural details have given it an almost otherworldly appearance.
Its mysterious atmosphere has also attracted filmmakers and writers.
One internationally recognised example is the film adaptation of Dan Brown’s novel Inferno, which features the Basilica Cistern as an important location.
For many visitors, walking through the cistern feels like stepping into a hidden chapter of Istanbul’s history.
10. What Should You Look for When Visiting the Basilica Cistern?
The Basilica Cistern is best explored slowly. Instead of simply walking through the main visitor route, take time to observe the details.
Here are some of the highlights worth looking for:
The Medusa Heads: Find the two unusual Roman sculptures in the northwestern section of the cistern. Observe their different positions and consider the possible explanations behind them.
The Weeping Column: Look closely at the unusual carvings resembling tears and eyes. It is one of the most distinctive columns in the structure.
The 336 Columns: Notice how the columns differ in material, style, and decoration. Their variety reveals the ancient practice of reusing architectural elements.
The Brick Vaults: Look upwards to appreciate the engineering behind the structure. The brick arches and vaults distribute the enormous weight above the cistern.
The Water Reflections: Observe how the columns are reflected in the shallow water. The lighting creates an impression of an endless underground space.
These details help visitors appreciate the Basilica Cistern not only as a tourist attraction but also as an extraordinary example of Byzantine engineering.
Frequently Asked Questions About the Basilica Cistern
Why was the Basilica Cistern built?
The Basilica Cistern was built during the reign of Emperor Justinian I around 532 AD to store water for the Great Palace and surrounding imperial buildings in Constantinople.
Why are the Medusa heads upside down?
The exact reason is unknown. Some legends suggest that the heads were turned to neutralise Medusa’s mythical power, while a more practical explanation is that they were reused as convenient column bases.
What is the Weeping Column in the Basilica Cistern?
The Weeping Column is a marble column decorated with tear-like and eye-shaped patterns. Local legend connects it with workers who died during construction, although this interpretation is not historically confirmed.
How many columns are inside the Basilica Cistern?
The Basilica Cistern contains 336 columns arranged in twelve rows of 28 columns each.
Who discovered the Basilica Cistern?
The cistern was brought to wider attention in the mid-16th century by French scholar Petrus Gyllius, who investigated reports of local residents drawing water from underground openings.
Was the Basilica Cistern used during the Ottoman Empire?
Yes. Following the conquest of Constantinople in 1453, it continued to supply water for a period, including to the gardens of Topkapı Palace.
Is the Basilica Cistern worth visiting?
Absolutely. It is one of Istanbul’s most distinctive historical attractions, combining Byzantine engineering, ancient Roman sculptures, mysterious legends, and an unforgettable underground atmosphere.
Final Thoughts: The Secrets Beneath Istanbul
Istanbul is famous for its mosques, palaces, historic streets, and magnificent views of the Bosphorus. But some of its most fascinating stories are hidden beneath the ground.
The Basilica Cistern is one of those places.
Its 336 columns, mysterious Medusa heads, legendary Weeping Column, and centuries-old water system reveal a side of Istanbul that many visitors never expect to discover.
Some of its mysteries may never be fully explained. Others become clearer when history and archaeology are examined together.
One thing is certain: beneath the streets of Sultanahmet lies a remarkable monument that connects modern Istanbul with the world of the Byzantine Empire.
Discover more fascinating stories and hidden historical places with Visit Istanbul.
