The Basilica Cistern, the largest Byzantine cistern

The Basilica Cistern, located in the Eminönü district of Istanbul, next to Hagia Sophia, was built to supply water to the city of Istanbul during the reign of Emperor Justinian I in the year 542. The main purpose of the cistern was to meet the water needs of the Grand Palace and its surrounding buildings.

The cistern was neglected when Constantinople was invaded by the Ottomans. In 1545, the Frenchman Petrus Gyllius rediscovered the cistern when inhabitants told him that they could obtain water by lowering buckets into a dark space beneath their basement. In 1985, the cistern was cleaned and renovated by the Istanbul Metropolitan Municipality.

The Basilica Cistern has become a famous historical site that attracts millions of tourists every year. It is around 140 metres long and 70 metres wide, covering an area of 9,800 square metres. The great cistern is made up of 336 columns, 9 metres long and around 4 metres apart.

The site opened its doors to tourists in 1987 after the Istanbul Metropolitan Municipality carried out major repairs. Also known as the Underground Palace, the large structure of marble pillars is a great tourist experience.

With a floor plastered with a thick layer of mortar to make it water-resistant, the cistern is supported by 336 pillars, each 9 metres high, placed at identical distances. Each of the cistern's columns is different, with finely sculpted marble capitals. The basilica cistern is reached by a 52-step staircase.

The capitals of the pillars are Ionic or Corinthian, but some are Doric. One of the pillars has an engraving of a hen's eye with tears and inclined branches. It pays tribute to the slaves who lost their lives during the construction of the basilica cistern.

Two pillars in the north-western part of the cistern rest on Medusa's heads. Archaeologists believe that they were brought in to be used as supports for the pillars. According to Greek mythology, Medusa was one of the three Gorgons and a sea nymph. After a relationship with Poseidon in Athena's temple, he transformed her into a demon with snakes for hair. If you were unfortunate enough to meet her gaze, she turned everything to stone.

The heads are placed sideways and upside down. Some believe that Medusa's heads were used in the ancient world to ward off evil, while some historians think that it was the emperor's way of declaring that the pagan gods had died for him.

With its mystical atmosphere and historical value, the cistern is not only a favourite with tourists. This architectural beauty frequently attracts the attention of artists. Some popular films feature scenes from the Basilica Cistern, such as the third James Bond film, Skyfall. In addition, the cistern has lent its image to music videos, photo shoots and even popular video games such as "Assassin's Creed Revelations".