Stunning underground cistern draws tens of thousands of tourists a day in Istanbul

It may look like an ancient palace or place of worship, but this stunning structure had a more mundane function: storing water.

Situated 20 meters (65 ft.) below ground, the cavernous and structure is a relic of past civilizations.

Known as the Basilica Cistern, it was built during the Byzantine Empire and reached its present state under Emperor Justinian who reconstructed it in the 6th century.

The 10,000 sq. meter (105,000 sq. ft.) subterranean maze of columns was a storage space for water that sustained not only the Byzantine Imperial Palace, but the entire city of Constantinople.

After the fall of the city to the Ottomans in 1453, the cistern continued to serve the new ruling sultans in the burgeoning city of Istanbul.

Along with the Hagia Sophia, which is only 150 meters (500 ft.) away, it’s among present-day Istanbul’s top tourist destinations.

Since reopening its doors in July 2022 after an ambitious renovation, the cistern welcomes some 20,000 to 30,000 visitors every day, according to Istanbul Greater Metropolitan Municipality’s Department of Cultural Assets Conservation.

A popular sight is the Crying Column, so named because it appears to be wetter than the other columns and is adorned by teardrop-shaped patterns.

The cistern also acts as a makeshift gallery for artists who are given the opportunity to display their work among the 9-meter (30 ft.) columns.

Visitors make their way through the area by walking on a metal grate path set just a few feet above the water below.

Once in a while, they’re struck by a droplet of water that falls from the condensation, an ironic reminder of the nearly 1,500-year-old cistern’s ancient purpose.

"I just can’t believe that those many years ago that they had this much knowledge to build something like this and make it watertight and find the resources," says Tracey Vincent, a visitor from New Zealand as she makes her way through the structure.

More than 300 Ionic, Corinthian and Doric columns support the domed roof of the underground reservoir.

Most were brought over from other, older structures across the empire and recycled, giving the cistern its uniquely mismatched character encompassing architectural examples of the Byzantine and Roman eras.

"Although we say that the Basilica Cistern dates back to the 6th century, it is a qualified structure that contains special repurposed material dating back much earlier, perhaps to the 4th century," explains Oktay Ozel, Head of Istanbul Greater Metropolitan Municipality’s Department of Cultural Assets Conservation.

One of the most striking sights is the two overturned heads of Medusa, a Greek mythological figure who was often depicted as having a mass of snakes on her head instead of hair. Legend has it she could turn people into stone just by looking at them.

It’s a mystery, and no one knows for sure, but some theories suggest the Medusa heads were purposefully positioned to deactivate her petrifying abilities.

Local authorities are clearly very proud of the Basilica Cistern and not only because it pulls in huge numbers of visitors.

"The Basilica Cistern is naturally a symbolic building for Istanbul," says Ozel.

"It’s a special historic site that is the apple of our eye."