Upside down Medusa head in The Basilica Cistern (Yerebatan Sarnıcı) in Istanbul

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. There is no written evidence that suggests they were used as column pedestals previously. Tradition has it that the blocks are oriented sideways and inverted in order to negate the power of the Gorgons' gaze.