A
bunker is a defensive military fortification designed to protect people or valued materials from falling bombs or other attacks. Bunkers are mostly underground, compared to
blockhouses which are mostly above ground. They were used extensively in
World War I,
World War II, and the
Cold War for weapons facilities, command and control centers, and storage facilities (for example, in the event of
nuclear war). Bunkers can also be used as protection from
tornadoes.