The Basilica Cistern, Istanbul Turkey

The Basilica Cistern (Turkish: Yerebatan Sarayı - "Sunken Palace", or Yerebatan Sarnıcı - "Sunken Cistern"), is the largest of several hundred ancient cisterns that lie beneath the city of Istanbul (formerly Constantinople), Turkey. The cistern, located 500 feet (150 m) southwest of the Hagia Sophia on the historical peninsula of Sarayburnu, was built in the 6th century during the reign of Byzantine Emperor Justinian I. The name of this subterranean structure derives from a large public square on the First Hill of Constantinople, the Stoa Basilica, beneath which it was originally constructed. Before being converted to a cistern, a great Basilica stood in its place, built between the 3rd and 4th centuries during the Early Roman Age as a commercial, legal and artistic center. Located in the northwest corner of the cistern, the bases of two columns reuse blocks carved with the visage of Medusa. The origin of the two heads is unknown, though it is thought that the heads were brought to the cistern after being removed from a building of the late Roman period. According to popular myth, Medusa was one of the three Gorgons, the terrifying female creatures from Greek Mythology. Legend has it that Medusa, with her hair of snakes could turn anyone who looked at her into stone, and therefore images of Gorgons were used to protect great buildings. Another version of the story claims that Medusa was the only mortal Gorgon, a beautiful girl with long hair and dark eyes who had long been in love with Perseus, the son of Zeus. Athene, also in love with Perseus, turned Medusa's hair into snakes in a jealous rage. From then on, every person Medusa looked at was petrified. After learning of Medusa's curse, Perseus beheaded her, taking her head to war with him and turning his enemies into stone. It is said that many Byzantium era sword handles and columns were engraved with her head upside down. http://en.wikipedia.org/wiki/Basilica_Cistern