|The Basilica Cistern, also known as the “Sunken Palace” or “Yerebatan sarayi” in turkish,, was constructed by Justinian in 532 to supply water to the Byzantine Palace primarily.
Basilica cistern or better known as Yerebatan sarayi is a very authentic place and a must see in Istanbul. The cistern is located at the Sultanahmet square, when you are about to reach the Sultanahmet Square on the right bank you will see the basilica cistern. There is a small building next to the tram line, there leads the stairs down to the Basilica cistern. Basilica is open every day from 09:00 hrs to 18:30 and the entrance fee is 10 TL (~7 USD) for foreign visitors.
Underground waterway was used as a reservoir for water storage for the Great Palace and other buildings. It is 132 m length, by 65m wide. There are 336 columns in the cistern. Most of the column capitals are either in Corinthian or Doric Style.
Walk to the back of the Cistern, and you will find one upside down Medusa head supporting one of the columns. Why it is upside down has been a question of much discussion, but the best guess is that the people who placed the stone believed that if the head was upside down, it would ward off evil spirits.
Not far from the upside-down Medusa head is a second Medusa head, which is sideways. Why one head is upside down and the other is sideways only deepens the question about their orientation. Perhaps the builders felt that to place two heads in the same orientation would empower the evil forces living in the snakes on Medusa’s head. Also, their presence in the Cistern in the first place is interesting. Perhaps, since they were underwater for most of the ages, the evil forces remained safely submerged.
Today it has been completely renovated. Water still drips melancholically through the ceiling, and the brick-domed ceiling echoes classical music.
For more info visit official site of the cistern with different language options.