Visit the Basilica Cistern, originally built in the 4th century and expanded in 532 AD, a vast underground reservoir from the Byzantine era. Discover the atmospheric chamber, its forest of marble columns, and the famous Medusa heads inspired by Greek mythology. Explore this cathedral-size cistern, built during the reign of Emperor Justinian I in 532 A.D. to supply water to the Great Palace. It stores up to 80,000 cubic meters of water, delivered via 20 kilometers of aqueducts from a reservoir near the Black Sea. Descend the fifty-two stone steps into the entrance of the cistern. The cistern is surrounded by a firebrick wall with a thickness of 4 meters, coated with a waterproofing mortar. Hear how the Basilica Cistern's water comes from the Eğrikapı Water Distribution Center in the Belgrade Forest and travels through the 971-meter-long Valens Aqueduct and the 115-meter-long Mağlova Aqueduct, built by the Emperor Justinian.