A bunker is a fortified underground shelter designed to protect people and equipment from military attacks, natural disasters, or other emergencies. These structures are often built with thick walls and reinforced ceilings to withstand explosions and provide safety. Bunkers can be found in various forms, from simple shelters to complex facilities with living quarters, storage, and utilities. Bunkers have been used throughout history, especially during wartime, to safeguard military personnel and civilians. They are commonly associated with World War II and the Cold War, when fears of nuclear attacks led to the construction of many underground facilities. Today, some bunkers are repurposed for use as survival shelters or even luxury retreats.