Archaeologists have discovered an entire underground city beneath Hagia Sophia in Istanbul, and the scale of it caught e...

Archaeologists have discovered an entire underground city beneath Hagia Sophia in Istanbul, and the scale of it caught even the experts off guard. It started in early 2025 during routine maintenance work in the atrium of Hagia Sophia, the courtyard that preceded the original church. Workers uncovered a series of partially buried vaults, and what began as a technical job quickly turned into one of the most significant archaeological finds in Istanbul in years. Excavations revealed six independent but interconnected underground structures beneath the atrium alone. Among the most striking finds is a tunnel stretching over 160 meters in length, which predates the reconstruction of Hagia Sophia under Emperor Justinian in the 6th century. That means parts of this underground network were built before the iconic structure standing above it today. The structures span multiple eras, from Late Antiquity through more recent periods. Researchers identified circulation and maintenance tunnels, hydraulic systems, water channels, vaulted chambers, and spaces that may have been used for storage or ritual activity. Seven distinct Byzantine tunnel lines, each estimated at around 1,600 years old, have been documented connecting different chambers. Broader surveys suggest the underground network extends well beyond what has been excavated so far. Some findings point to interconnected corridors exceeding one kilometer in total length, forming a labyrinth beneath the entire religious complex. Turkish authorities confirmed the excavations will continue under strict scientific supervision, and some sections could eventually be opened to the public. The discovery reveals a level of Byzantine engineering far more complex than anyone had anticipated, with a structure that was clearly adapted and expanded across centuries. #HagiaSophia #Byzantium #Archaeology