Musée des Égouts de Paris

Beneath the streets near the Pont de l'Alma, this unusual museum leads visitors into the working sewers of Paris, a vast subterranean network largely built during the Second Empire under the engineer Eugène Belgrand. Walkways run alongside the flowing channels, with displays explaining the history of the city's water supply, drainage and the giant machines that clean the tunnels. The sewers famously feature in Victor Hugo's Les Misérables. The damp, echoing galleries reveal hidden urban infrastructure.