Classical music echoing off the still water and the seductive lighting make your descent into the "Sunken Palace" seem like a scene out of Phantom of the Opera. The only thing missing is a rowboat, which was an actual means of transportation before the boardwalk was installed in what is now essentially a great underground fishpond and stunning historical artifact. The cistern was first constructed by Constantine and enlarged to its present form by Justinian after the Nika Revolt using 336 marble columns recycled from the Hellenistic ruins in and around the Bosphorus. The water supply, routed from reservoirs around the Black Sea and transported via the Aqueduct of Valens, served as a backup for periods of drought or siege. It was left largely untouched by the Ottomans, who preferred running, not stagnant, water, and eventually used the source to water the Topkapi Gardens. The cistern was later left to collect silt and mud until it was cleaned by the municipality and opened to the public in 1987. The water is clean and aerated thanks to a supply of overgrown goldfish that are replaced every 4 years or so.

Follow the wooden catwalk and notice the "column of tears," a pillar etched with symbols resembling tears. (An identical pattern is visible on the columns scattered along the tramway near the Üniversite stop, where the old Byzantine palace was once located.) At the far end of the walkway are two Medusa heads, one inverted and the other on its side; according to mythology, placing her this way caused her to turn herself into stone. Another superstition is that turning her upside down neutralizes her powers. Possibly, the stones were just the right size as pedestals.