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abandoned abstract accident admittance ammunition anti army assault attack background bank banking blast blastproof bomb bombs building bulletproof bunker burglary closed concept concrete construction danger dangerous deepearth defence device door doors empty entrance entry explosion explosive fallout fight fort fortification game games green handle heavy history insurance intro iron lock locked metal metaphor military no nuclear object proof protect reinforced safe safety secret secure security shelter stain stained storage strategy strong symbol theft underground war warfare weaponry weapons westerplatte