Underground Passages of Laon's Citadel
Laon is built upon the limestone quarries it mined over the centuries. The underground passageways that served as a prison in the Middle Ages were later, under Louis-Philippe, part of the town's defence system. The citadel was used as a military quarters and hospital for German troops during the First World War. Beneath the citadel, which is now an administrative building, traces of these miles of passageways remain, spread over three levels. A 450m-long stretch takes you into the bowels of the city.
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