Looks like it is currently closed, but from an interesting infrastructure standpoint, the Musée des Égouts de Paris (sewers underneath Paris). https://en.wikipe

Looks like it is currently closed, but from an interesting infrastructure standpoint, the Musée des Égouts de Paris (sewers underneath Paris). https://en.wikipedia.org/wiki/Paris_Sewer_Museum https://en.wikipedia.org/wiki/Paris_Sewer_Museum