The Hagia Sophia, a historic landmark in Istanbul, has revealed a hidden network of seven underground tunnel lines, estimated to be around 1,600 years old. This discovery, made during a restoration campaign, adds a tangible layer to the long-standing stories about the monument's subterranean secrets. The tunnels were found alongside a hypogeum, an underground burial complex, during cleaning and survey work in the garden areas surrounding the structure. The restoration program, led by Turkey's Culture and Tourism Minister Mehmet Nuri Ersoy, is being conducted under scientific oversight, with a focus on the building's long-term safety. The underground work is part of a larger, multi-stage restoration process that includes scanning, modeling, and material analysis across the site. During the cleaning operations, 1,068 tons of soil fill were removed, and another 102 tons were taken out from a separate underground burial area, revealing multiple underground 'spaces' and linked tunnels in the western and northern garden areas.
This isn't the first time the Hagia Sophia's underground story has come to light, but the latest documentation is unusually concrete. Named tunnel 'lines' and measured spoil removed, along with on-site visual records, have been made public. Professor Hasan Fırat Diker, who has worked on mapping and understanding the monument's below-ground infrastructure, emphasizes that the tunnel and culvert systems are crucial for ventilation and water management, not just romantic 'escape routes'. These practical functions help explain why much of the underground fabric is close to the structure's foundations and gardens, rather than forming a single, straight passage.
The restoration work is not happening in isolation but is accompanied by major efforts above ground, including scaffolding, façade cleaning, and structural checks, all intended to preserve the building for centuries. Minister Ersoy emphasizes the scientific process, stating that no work is done without scientific assessments and contemporary restoration requirements. This is particularly important at Hagia Sophia, where earlier interventions introduced materials like cement-based plasters, now deemed inappropriate for historic stone and brick. The timing of the restoration also reflects a broader concern: Istanbul's earthquake risk and the need to understand the monument's foundation, as the city was built with water below its feet.
The Hagia Sophia's 'underground' is part of a much larger Istanbul reality, shaped by cisterns, conduits, and storage systems that once supplied palaces, churches, and neighborhoods. The present Hagia Sophia was built in 532-537 AD under Emperor Justinian I, after earlier churches on the site were damaged or destroyed. It has been repeatedly repaired following earthquakes, making hidden infrastructure essential to its survival. The Basilica Cistern, located nearby, offers a public example of how Byzantine Istanbul managed water on a vast scale, making the tunnel-like maintenance spaces around major monuments plausible. The newly documented tunnel lines may help researchers understand how drainage, humidity, and maintenance were handled in different phases, including the Byzantine, Middle Byzantine, and Ottoman periods, without relying solely on myths.
The discovery of these ancient tunnels adds a new dimension to our understanding of the Hagia Sophia's history and architecture, highlighting the importance of scientific restoration and the hidden world beneath one of the world's most iconic landmarks.
