Overview
The Basilica Cistern (Yerebatan Sarnıcı, "Sunken Cistern") lies a few metres below street level in Istanbul's Sultanahmet district, a short walk from Hagia Sophia and the Blue Mosque. Emperor Justinian I built it in the 6th century CE to store filtered water for the Great Palace and nearby buildings. The name "Basilica" comes from a public square that once stood above.
The chamber measures about 138 by 65 metres and can hold roughly 80,000 cubic metres of water. Three hundred thirty-six columns — mostly Ionic and Corinthian capitals recycled from earlier structures — rise from the floor in twelve rows. Two columns rest on carved Medusa heads, one inverted and one sideways, probably placed for size rather than superstition though legends flourish. Walkways installed in the 1980s let visitors circle the forest of columns above ankle-deep water stocked with carp.
Ottoman sultans maintained the cistern until modern pipes made it redundant; it was forgotten by many until the French scholar Petrus Gyllius rediscovered it in 1545. Today it is a museum and occasional concert venue. Its cool, mirrored darkness offers a radically different sensory experience from the sunlit domes overhead.