From the 1820s the quarry voids were put to a new use as mushroom fields: damp and dark, they provided the perfect growing spaces for fungi, which sprouted from rows of horse manure. Adaptable quarrymen made a career move into mushroom farming, and a subterranean Horticultural Society of Paris was founded, its first president being a former general inspector of the mines. At the height of the industry there were some 2,000 mushroom farmers working underneath Paris.
