By Shannon Lane @Shannonroselane

UNDERNEATH the ancient city of Istanbul is a cathedral-sized secret which the tourists rarely see

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Istanbul's tube line is is the second oldest underground rail system in the world

Measuring approximately 138 metres by 65 metres (105,000 sq ft), the Basilica Cistern is the largest of several ancient cisterns which lie beneath the city of Istanbul.

Istanbul was founded circa 330 CE as "Constantinople" a Roman City

The cistern was built by 7,000 slaves, instructed by Byzantine Emperor Justinian I in 532 A.D, and is supported by 336 marble columns, each measuring 9 metres in height.

One of the cisterns most famous aspects are the two Medusa heads used as column bases, one positioned on its side, and the other upside down. It is speculated that the positioning of these heads is to avoid the evil gaze of Medusa, however it is also believed that these heads were positioned this way due to their sizing.

Above ground the city is busy and bustling

The enormous cistern was forgotten for centuries and only accidently rediscovered by the Frenchman Peter Gyllius in 1545.

The Basilica Cistern was restored in 1985

Urban explorer and ‘dark tourist’ Darmon Richter investigated the city’s cisterns for himself in 2015.

Platforms were built to replace the boats once used to tour the cistern
The Medusa heads were recycled from an ancient Roman building

He said: "Istanbul has a lot of Roman architecture to see, but most of the structures above ground are surrounded by modern buildings.

"The 4th Century Valens Aqueduct, for example, now has a six-lane highway going between its arches!

The cistern is quiet during off-peak tourist times

"I was really interested to see the cisterns because it gave me a chance to get away from the chaos of the modern city – and in the silence, underground, it’s much easier to get lost in the city’s past."

The cistern is capable of holding 100,000 tons of water

Although capable of holding 100,000 tonnes of water, after reconstruction in the 1980’s, the cistern now only contains a few feet of water; filled with fish and tourist’s wishing pennies.

Damon said: "As well as visiting the popular cisterns, I really enjoyed just walking around the older areas of the city and finding parts of ancient walls, entrances to tunnels, and little clues to the massive underground structures which still hide beneath the surface of Istanbul.

The cistern was used as a location for the 1963 James Bond film

"One time I got talking to a local, and he gave me an unofficial tour of some Byzantine tunnels near the waterfront. The entrance was completely unsealed... you just needed to know where to look.”

See more of Darmon Richter’s explorations at