The Incredible Basilica Cistern of Istanbul

February 7, 2024

When Istanbul was Constantinople during the period of the great Roman, and later Byzantium Empire, hundreds of subterranean cisterns were built underneath the streets and houses to store water. The largest and the grandest of them all is the Basilica Cistern, so called because it lay beneath the Stoa Basilica, a large Byzantine public square. This impressive structure with more than three hundred vaulted columns topped with Corinthian or Doric capitals appears like a palace, earning the cistern its modern nickname of the “Sunken Palace”. Locally, it’s known as Yerebatan Sarnıcı, Turkish for “underground cistern”.

The cistern was commissioned by Emperor Justinian I and built in 532 to meet the water needs of the Great Palace and adjacent buildings. It is 140 meters long and 70 meters wide, and had a storage capacity of 100,000 tons. The ceiling is supported by a forest of 336 marble columns, each 9 meters high and arranged in precise rows and columns. Many of these columns were salvaged from ruins of older buildings, likely brought to Constantinople from various parts of the empire, together with those that were used in the construction of Hagia Sophia.

Photo credit: Marc Garrido Clotet/Flickr

Perhaps the most striking sight in the cistern are two giant heads of the mythical monster Medusa. The Medusa heads are used casually as supports under the two columns at the northwest edge of the cistern. One of them is positioned upside down and the other is tilted to the side. Their strange positioning and the mystery of their origin attracts the most attention from visitors. It’s said that the heads were so placed to counter the deadly gaze of Medusa. However, the truth might be a bit more practical than mythical — this orientation provided proper support to the columns.

After Istanbul fell to the Ottoman conquest in 1453, the Ottomans established their own water facilities in the city because they preferred running water over still water. The cistern was closed and forgotten. Nearly a century later, when Dutch scholar Petrus Gyllius was in Constantinople researching Byzantine antiquities, he heard stories of how local residents near Hagia Sophia were able to obtain water by lowering buckets into holes in their basement. Sometimes they even caught fish. Gyllius decided to investigate and eventually managed to access the cistern through the basement of one of the houses in that area. Even after the discovery, the Ottomans didn’t treat the cistern with respect and turned it into a rubbish dump.

Once it was possible to tour the underground cistern on a boat, just like James Bond did in the 1963 movie From Russia with Love. In 1985, during restoration work, some 50,000 tons of mud were removed from the cistern and elevated platforms built throughout to replace the boats. The cistern was opened to the public in 1987.