The city revealed beneath Hagia Sophia – and the enigmatic room with no explanation

Cleaning work beneath Hagia Sophia in Istanbul has uncovered a vast underground network stretching about nine kilometers, including water channels and a mysterious structure known as 'Structure 6' – a complex with arches and eight hidden niches without water pipes, whose purpose remains a puzzle.

Extensive cleaning and restoration work beneath Hagia Sophia in Istanbul has revealed a vast underground network stretching about nine kilometers. The research, led by Professor Hasan Fırat Diker and published in the journal Open Archaeology, involved the removal of some 300 tons of soil and debris. Most of the spaces were used for water management and transport, but one structure, known as 'Structure 6', is anomalous: it includes arches, a vaulted passage, a hidden wall, and eight rectangular niches, but no trace of terracotta pipes. Researchers describe it as 'enigmatic'. Hagia Sophia, built between 532 and 537 AD by Emperor Justinian I, conceals complex infrastructure built over generations. Researchers estimate that large parts of the passages remain blocked.