The Basilica Cistern, located close to the Hagia Sophia, is the largest of many cisterns under the streets of Istanbul. The cistern is 105,000 square feet and can hold up to 2,800,000 cubic feet of water. Although the cistern is not filled completely with water, fish swim through the dark and shallow water. It is believed that the two column bases depicting Medusa's head resting in the back of the cistern were removed from a Roman building and placed sideways in the cistern to prevent the power of Medusa's eyes.
