Nearly 9 kilometers of hidden tunnels beneath Istanbul's Hagia Sophia Grand Mosque are being uncovered as part of ongoing restoration and conservation efforts, with around 3,000 tons of mud and debris already removed from the historic site, Turkish media reported on Tuesday.
Culture and Tourism Minister Mehmet Nuri Ersoy spoke to reporters during the Antalya Culture Route Festival, organized by his ministry for the fourth time this year and which began Monday.
Ersoy said the ministry was carrying out the most comprehensive restoration, conservation and reinforcement works at Hagia Sophia in the history of the Turkish Republic. Members of the scientific committee have described the project as one of the most extensive interventions since the time of Ottoman architect Mimar Sinan, he added.
Reinforcement work has begun not only on the main dome but also on the eastern semi-dome, where the mihrab and minbar are located, Ersoy said.
He noted that the work was being conducted in line with the recommendations of the scientific committee, the conservation board and universities. He also stressed that meticulous engineering efforts were underway to preserve the building's original architectural features while keeping it open to worshippers and visitors.
Ersoy said research and extensive work were also continuing in Hagia Sophia's underground historical areas. So far, approximately 3,000 tons of mud and debris have been removed, while historic tunnels, water channels and underground chambers are being examined.
As work progresses, teams have discovered additional spaces in some sections, he said.
"These structures also provide important insights into Istanbul's historical water management and infrastructure. We are investigating underground systems that served functions such as rainwater drainage and water distribution. Some sections are large enough for people to walk through. The underground world of Hagia Sophia is at least as fascinating as the structure above ground," Ersoy said.
He added that the work would help reveal historical layers of Hagia Sophia that are not currently visible.
"We are preserving Fatih's legacy through a holistic approach, from its dome to its underground structures," he said, referring to Ottoman Sultan Mehmed II, known as Mehmed the Conqueror, who captured Istanbul in 1453.
The Hagia Sophia Grand Mosque stands in Istanbul's historic Sultanahmet district, an area shaped by successive civilizations and home to important Byzantine and Ottoman heritage sites, including the ancient Hippodrome and Basilica Cistern. Its underground structures are part of a broader historical landscape reflecting centuries of urban development, water management and architectural transformation. Hagia Sophia and the surrounding historic areas were added to UNESCO's World Heritage List in 1985.