Neak Pean or Neak Poan (the entwined serpents) is an artificial island with a Buddhist temple on a circular island in Preah Khan Baray built during the reign of King Jayavarman VII. Neak Pean probably represents Anavatapta, a mythical lake in the Himalayas whose waters are thought to cure all illness.
Neak Pean was originally designed for medical purposes (the ancients believed that going into these pools would balance the elements in the bather, thus curing disease), it is one of the many hospitals that Jayavarman VII built. It is based on the ancient Hindu belief of balance. Four connected pools represent Water, Earth, Fire and Wind. Each is connected to the central water source, the main tank, by a stone conduit presided over by one of Four Great Animals: Elephant, Bull, Horse, and Lion, corresponding to the north, east, south, and west quarters.