The Basilica Cistern, a historical landmark, is situated to the southwest of Hagia Sophia. Constructed in the 6th century under the reign of the Byzantine Emperor Justinian I, this cistern stands as a testament to the architectural prowess of the time. Today, it is open to the public, offering visitors a unique experience. Visitors can explore the intricately engraved marble columns and vaulted ceilings, and immerse themselves in its eerie ambience, accentuated by dripping water and swimming fish. The Basilica Cistern also serves as a venue for regular artistic exhibitions, adding to its cultural significance.