I see your secure Swedish parking/bunker and raise you the Moscow subway system that has multiple stations built as a emergency shelters, with huge doors embedd

I see your secure Swedish parking/bunker and raise you the Moscow subway system that has multiple stations built as a emergency shelters, with huge doors embedded into walls that can seal the interior and incospicuous regular-sized doors on each side of these, fronting airlock-like bypasses to allow for scouting the outside when needed. There are several types - swinging, sliding and even draw-bridge like - all still presumably in operational state. [1] http://yablor.ru/blogs/vorota-v-podzemnuyu-citadel/1000940 http://yablor.ru/blogs/vorota-v-podzemnuyu-citadel/1000940 (in Russian, but images are self-explanatory).