Picture of the Day 09/28/26 - Wikimedia Commons

View of the Basilica Cistern, Istanbul, Turkey. The Basilica Cistern, or Cisterna Basilica is the largest of several hundred ancient cisterns that lie beneath the city. This subterranean cistern was called Basilica because it was located under a large public square, the Stoa Basilica, on the First Hill of Constantinople. The cistern, built in the 6th century during the reign of Byzantine emperor Justinian I, provided a water filtration system for the Great Palace of Constantinople and other buildings on the First Hill, and continued to provide water to the Topkapı Palace after the Ottoman conquest in 1453 and into modern times. Today it is kept with little water, for public access inside the space.

Diego Delso, CC BY-SA 4.0, via Wikimedia Commons. View source.