The Hagia Sophia's underground network: Unveiling a 1,600-year-old mystery beneath Istanbul's iconic landmark.
The restoration of Hagia Sophia has unveiled a hidden network of seven underground tunnel lines, dating back around 1,600 years. This discovery adds a fascinating layer to the monument's history, shedding light on the intricate underground world beneath one of the world's most iconic structures. The tunnels were found during cleaning and survey work in the garden areas, alongside a hypogeum, an underground burial complex. The find highlights the importance of scientific oversight in the conservation program, with the building's long-term safety as a key focus.
A hidden network from the early Byzantine era
Turkey's Culture and Tourism Minister, Mehmet Nuri Ersoy, emphasized that the tunnel work is part of a larger, multi-stage restoration process. This includes scanning, modeling, and careful material analysis across the site. During the cleaning operations, seven tunnel lines were documented, and 1,068 tons of soil fill were removed, while another 102 tons were taken from a separate underground burial area. The report also describes multiple underground 'spaces' and linked tunnels in the western and northern garden areas.
The underground story of Hagia Sophia is not new, but the latest documentation is highly detailed. Professor Hasan Fırat Diker, an expert in mapping and understanding the monument's below-ground infrastructure, has previously described the tunnel and culvert systems as crucial for ventilation and water management, not just romantic 'escape routes'. These practical functions explain why the underground fabric is close to the structure's foundations and gardens, rather than forming a single, straight passage.
Restoration and the underground context
The restoration work is not just about preserving the building above ground; it also involves major efforts below. Scaffolding, façade cleaning, and structural checks are intended to protect the building for centuries. Minister Ersoy stressed the importance of scientific assessments and contemporary restoration requirements, a crucial consideration at Hagia Sophia, where earlier interventions used 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. The city's history includes dome collapses and major repairs after earthquakes, with modern engineers focusing on vulnerable structural points while avoiding heavy-handed interventions. The work's logic is often subterranean, focusing on load paths, drainage, humidity control, and foundation health.
The deeper context: A city built with water below its feet
Hagia Sophia's underground is part of a larger Istanbul reality, a historic city shaped by cisterns, conduits, and storage systems that once supplied palaces, churches, and neighborhoods. The present Hagia Sophia, built in 532-537 AD under Emperor Justinian I, has been repaired repeatedly after earthquakes, making hidden infrastructure essential for survival. The Basilica Cistern, a short walk away, is a public example of Byzantine Istanbul's water management, making the tunnel-like maintenance spaces around major monuments highly plausible.
The newly documented tunnel lines may help researchers understand how drainage, humidity, and maintenance were handled in different phases, from Byzantine to Ottoman, without relying solely on myths. This discovery adds a new dimension to our understanding of Hagia Sophia's history and the city's ancient water management systems.
