Everyone visits the Louvre, so surprise your friends back home by telling them you toured the infamous 19th-century sewers of Paris. Brave their unpleasant though tolerable smell (it's worse in the height of summer) to follow an underground display describing the passages and footbridges famously immortalized as the escape routes of Jean Valjean in Les Misérables and the Phantom of the Opera. Signs indicate the streets above you, and detailed panels illuminate the history of waste disposal in Paris, whose sewer system is the second largest in the world, after Chicago's.
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