Subterranea

underground lake salt cavern subterranean river rock-cut architecture subway underground structure deep geological repository underground city burial vault storm cellar Svalbard Global Seed Vault cavern volcanic pipe basement underground parking space underground storage lunar lava tube lava tube sump London deep-level shelters cave crawl space Stepney Green cavern Almería air raid shelters Camden Catacombs Cueva de Conan Kingsway telephone exchange cave system hypogeum wine cave missile launch facility casemate dungeon dugout Los Angeles Mall