As far as we know, the 30 Years War (1618-48) was held responsible
for the longest occupation of the caves by the inhabitants (who
were fleeing Amiens, Doullens and Arras as Jean de Weerd’s and Prince
Thomas’s troops were advancing).
Between 1750 and 1830, salt-smugglers used parts of the caves
as salt-cellars until the salt-tax officers had departed. During
harsh winters women gathered down there and span in the evenings.
The most destitute took advantage of the protective caves and
relative warmth against bad weather.