1,600-year-old underground tunnels discovered under Hagia Sophia during restoration

Previously unknown underground tunnels dating back around 1,600 years have been uncovered beneath Hagia Sophia during ongoing restoration work. The discovery sheds new light on the monument’s early Byzantine infrastructure.

Türkiye’s Culture and Tourism Minister Mehmet Nuri Ersoy announced that conservation efforts are progressing under strict scientific supervision. Scaffolding has been installed across large sections of the structure, while material analysis revealed layers from the Early Byzantine, Middle Byzantine and Ottoman periods. Traditional handmade bricks are now being used in repairs, and ground-penetrating radar surveys have helped guide structural reinforcement.

Work has focused heavily on strengthening the dome and minarets. Stones from one minaret were carefully dismantled, restored and reassembled. Inside, a 43.5-meter scaffolding system was installed to protect mosaics and support dome restoration.

Excavation teams removed more than 1,000 tons of soil from underground tunnels and chambers extending hundreds of meters. Professor Hasan Fırat Diker stated that seven documented tunnel lines date to the early Byzantine period.

Blue Mosque restoration completed

Ersoy also confirmed that restoration of the Blue Mosque has been completed — the most comprehensive conservation effort in its 400-year history. The mosque remained open to worship throughout the project.

Repairs included structural reinforcement of all six minarets, renewal of 400 tons of lead roofing, restoration of domes and balconies, and conservation of stone and marble surfaces.