(CNN) -- Barmy about bunkers? Crazy about caves? From Congress's former nuclear shelter to the Viet Cong's tunnels and a Parisian necropolis, here are some of the world's best subterranean sights. Coober Pedy, South Australia Tourists wanting to channel their inner Hobbit should head to Coober Pedy. Most of the South Australian town's 3,000 residents live underground, where they frequent a subterranean church, restaurant, hotel and shops. The town produces 70% of the world's opal, and the blazing outback sun is the reason residents most prefer to live underground, as well as working there. Coober Pedy comes from the Aboriginal term "kupa piti," which means "white man's hole in the ground."
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In South Australia, a whole town lives underground to escape the heat
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Think Seattle's nice? Try the city beneath it
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Drainage systems sound dull but Tokyo's is an engineering marvel
Begun in 1992, the tunnels -- 50 meters deep and six kilometers long and growing -- contain pumps and tanks dedicated to keeping @placeholder dry during the rainy season.