Once they became mined out, the underground quarries of Caen stone generally presented no problems. They were excellent for producing mushrooms on a commercial basis. However, with pressure to build for an expanding population in the mid-20th century, many of the voids had to be filled in before building could take place. Several quarries, however, played an important and very positive role in the 1940s. During the bombardment of Caen by the Allies in 1944 these quarries provided safe refuge.
Although nearly 2000 inhabitants of the city died within two months of the D-Day landings on 6 June, many hundreds more owed their lives to the redundant quarries where their forefathers may have worked for many generations before them.