THE PARIS SEWERS (Paris, France)
A waste tunnel system was begun under the streets of the French capital in 1370, and has been expanded since. An unlikely place of romance and mystery, it was featured in Victor Hugo's Les Misérables, where it's called "the intestine of the Leviathan" and the "conscience of the city," a place where class distinctions become unimportant.
(Image courtesy Wikimedia Commons; CTTO)
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