Emergency Government Headquarters arenuclear fallout bunkers built by theGovernment of Canada at the height of theCold War during the infancy of the ICBMthreat. Scattered across the country, the shelters are popularly known as"Diefenbunkers", a nickname coined by Liberal opposition politicians of the early 1960s, and was derived from the name of the Prime Minister of the day, John Diefenbaker, who authorized their construction. Over fifty bunkers were built, including the many redundant Relocation Unit locations as well as retrofitted buildings that comprised many Zone Emergency Government Headquarters locations. Most of these facilities were built, often in great secrecy, at rural locations outside major cities across Canada. The majority of the larger facilities were two-storey underground bunkers while the largest at CFS Carp had four floors; these facilities were designed to withstand a near-miss from a nuclear explosion. Each underground facility had entrances through massive blast doors at the surface, as well as extensive air filters and positive air pressure to prevent radiation infiltration. Underground storage was built for food, fuel, fresh water, and other supplies for the facilities which were capable of supporting several dozen people for a period of several weeks.