Basilica Cistern was built in the 5th century under the reign of Emperor Justinian. It is the largest surviving Byzantine cistern in Istanbul. The cistern was constructed using 336 columns, many that were salvaged from ruined temples. It provided a water filtration system for the Great Palace of Constantinople and other buildings on the First Hill.
One of two Medusa heads from the cistern used as the base of a column
In 1985, the Istanbul Metropolitan Municipality cleaned and renovated the cistern and opened it to the public in 1987. It has since become one of Istanbul’s most popular attractions.
It really is a cool site and I really enjoyed it. Bond fans might remember it as a location in “From Russia with Love.”