In the colossal, cathedral sized water tank beneath the Hagia Sophia in Istanbul, Turkey, several heads of Medusa have been used as pillar bases for the past 1.500 years. It is not entirely known where the heads came from, but they were believed to be taken from some other Roman ruin. The heads are upside down or sideways to inhibit the power of the Gorgon Medusa's gaze.
The water tank's existence was forgotten for hundreds of years, despite being beneath the Hagia Sophia. When it was rediscovered, explorers found fish inside of it.