YEREBATAN SARNICI Photos just moving around

The Basilica Cistern (Yerebatan Sarnıcı), located beside Hagia Sophia in Istanbul’s historic centre, is one of the most impressive surviving structures of Byzantine engineering. Constructed in the 6th century during the reign of Emperor Justinian I, the underground reservoir formed part of the vast water supply system that sustained Constantinople, the capital of the Byzantine Empire. Water was transported to the city through an extensive network of aqueducts and channels stretching deep into Thrace, then stored in large reservoirs and underground cisterns to ensure a reliable supply during periods of drought, siege, or rapid urban growth.

The cistern measures approximately 140 metres in length and 70 metres in width, with a storage capacity of around 80,000 cubic metres of water. Its interior is supported by 336 marble columns arranged in symmetrical rows, creating the appearance of a submerged underground basilica rather than a purely technical structure. Many of the columns and capitals were reused from earlier Roman buildings and temples, reflecting the Byzantine practice of incorporating architectural elements from older monuments into new construction. Brick vaults and arches distribute the immense weight of the ground and buildings above, while thick waterproofed walls protected the structure from leakage and structural failure.

The atmosphere of the cistern is defined by its dim lighting, reflections in shallow water, and monumental forest of columns. Among its most famous features are the two sculpted heads of Medusa used as column bases, one placed sideways and the other upside down. Their exact origin and symbolic purpose remain uncertain, adding to the mysterious character of the site. Forgotten for centuries after the Ottoman conquest, the cistern was rediscovered in the 16th century when travellers learned that local residents were drawing water and even catching fish through openings in their house floors above the hidden reservoir.

Today, the Basilica Cistern stands not only as a major historical monument, but also as evidence of the extraordinary scale and sophistication of Constantinople’s hydraulic infrastructure. Beneath the streets of modern Istanbul survives a hidden network of reservoirs, tunnels, and water systems that once sustained one of the world’s largest and most influential cities.

Find more about the Basilica Cistern.