Why Are There Medusa Heads Under the Basilica Cistern in Istanbul?

The Basilica Cistern in Istanbul contains two enormous carved Medusa heads used as column bases, one lying on its side and one placed completely upside down — and no surviving construction record explains why.

What Is the Basilica Cistern?

Built in 532 AD under the Byzantine Emperor Justinian I, the Basilica Cistern is an underground reservoir stretching roughly 105,000 square feet beneath the streets of Istanbul — about the size of two football fields. Its brick vaulted ceiling is supported by 336 marble columns arranged in 12 rows of 28, each column standing nearly 30 feet tall. At full capacity, the cistern held approximately 21 million gallons of fresh water, fed by aqueducts that piped it in from the Belgrade Forest about 12 miles away.

Most of those 336 columns were not purpose-built. They were salvaged from older structures scattered across the Roman Empire — a common Byzantine practice that gave the cistern an almost accidental grandeur. Old accounts record that some 7,000 laborers were put to work constructing it, though no detailed blueprints or engineering records have survived.

How Was the Cistern Rediscovered?

After the Ottoman conquest of Constantinople in 1453, the cistern gradually faded from official use and awareness. For a time, residents of the neighborhoods above had little idea what lay beneath them. The Flemish scholar Petrus Gyllius, visiting in the 16th century, made the remarkable discovery that locals were lowering buckets through holes cut in their own basement floors to draw water — and were even catching fish from the cistern below. His written account brought the structure back to European attention, though it had never truly been abandoned by those living directly above it.

What Are the Medusa Head Column Bases?

Two of the 336 columns rest on something entirely unexpected: massive carved stone heads of the Gorgon Medusa, repurposed from an earlier Roman structure. One head is positioned on its side; the other is placed fully upside down. They are the most visually striking feature of the cistern today and the source of its most enduring question.

No construction document, inscription, or official account explains why these particular blocks were oriented the way they were. Two competing explanations have circulated for centuries.

The practical theory holds that the builders simply rotated each enormous stone block to whatever angle allowed the column resting on top to reach the correct height and sit on a stable footing. The Medusa heads happened to be the right size and material — their orientation was an engineering solution, not a statement.

The mythological theory suggests the heads were deliberately turned to neutralize the Gorgon’s petrifying gaze. In Greek mythology, looking directly into Medusa’s eyes turned the viewer to stone — so placing the faces sideways or inverted was a way of rendering that power inert.

Both explanations are plausible. Neither has been proven. The builders left no note.

How Big Is the Basilica Cistern?

The cistern covers approximately 105,000 square feet — roughly 453 feet long and 212 feet wide. It held around 21 million gallons of water, making it one of the largest surviving cisterns from the ancient world. Istanbul (then Constantinople) relied on a network of underground cisterns for its water supply, and the Basilica Cistern was the grandest of them all.

Can You Visit the Basilica Cistern Today?

Yes. The Basilica Cistern, known in Turkish as Yerebatan Sarnıcı (“Sunken Cistern”), is one of Istanbul’s most-visited historical sites. Walkways allow visitors to move among the columns above a shallow layer of water, and lighting installations illuminate the brick vaults and the famous Medusa heads. It has also appeared in several films, most notably the 1963 James Bond film From Russia with Love.

The cistern is a living monument to what Byzantine engineering could accomplish — a vast, silent space built by thousands of hands, holding water in the dark beneath a city that never stopped moving above it. And at its base, two stone faces still stare into the floor and the wall, their reason taken with the people who placed them there.