A millennium-old subterranean reservoir has been unveiled in the historical district of Derbent. This architectural marvel, dating back to the 10th and 11th centuries, lay concealed beneath the earth for centuries before being integrated into a museum complex.  Extensive restoration efforts involved the removal of over a thousand cubic meters of water and an immeasurable amount of accumulated debris. Now, visitors to Derbent can descend into the depths and witness firsthand the intricate system that was used in medieval times to store and distribute water within the city.