The Basilica Cistern, also called the Yerebatan Sarayı or Yerebatan Sarnıcı, is the largest of several hundred ancient cisterns that still lie beneath the city of Istanbul, former Constantinople, Turkey.
This cathedral-sized cistern is an underground chamber of 143 by 65 metres, capable of holding 80,000 cubic metres of water. The large space is broken up by a forest of 336 marble columns each 9 metres high. The bases of two of these columns reuse earlier blocks carved with the head of a Medusa.
The cistern, located in the historical peninsula of Istanbul, was built by the Greeks during the reign of emperor Justinian I in the 6th century, the age of glory of Eastern Rome, also called the Byzantine Empire. The cistern is surrounded by a firebrick wall with a thickness of 4 meters and coated with a special mortar for insulation against water. The cistern's water was provided from the Belgrade Woods—which lie 19km north of the city—via aqueducts built by the emperor Justinian.
The cistern was used as a location for the James Bond film From Russia with Love. It is a popular tourist attraction.