Istanbul’s Byzantine Basilica Cistern contains 336 columns supporting its vaulted ceiling. The vast underground reservoir lies beneath the historic peninsula, close to Hagia Sophia, and is one of Constantinople’s best-known surviving waterworks.
The cistern was built during the reign of Emperor Justinian I in the sixth century, probably after the Nika riots of 532. It stored water brought into the city through aqueducts, helping supply the imperial district during periods when surface reservoirs or pipelines were vulnerable.
The columns are arranged in long rows and stand in water when the cistern is operating as a monument. Many were reused from earlier buildings, so their capitals and shafts are not completely uniform. Two famous column bases incorporate monumental Medusa heads, whose original purpose and position remain subjects of discussion.
The name “Basilica Cistern” reflects the earlier basilica that may have occupied the site above it. It should not be confused with the Binbirdirek Cistern, another large Byzantine reservoir in Istanbul.