If you are into unique experiences, you should definitely visit this establishment. Offering guided tours since 1889, this museum is truly one-of-a-kind.
The exhibitions focus on enlightening the public about the history of Parisian sewers, the role of sewer workers, the sanitation process and so on. You can also notice some references to Victor Hugo's Les Miserables, since one of the characters had to hide there while carrying his ally to safety. Overall, it is mostly suited for engineering geeks, as you get to see the behind-the-scenes of keeping such a huge city hygienic.
The sewers themselves are still in use. This exhibition is only for people who can tolerate unpleasant smells, as you will be walking above the sewers on metal grates. It is strongly advised not to touch anything and to wash your hands as soon as you leave. Bosquet-Rapp bus stop is right next to the building, lines 42 and 63. The entrance to the museum is a small booth that can be easily overlooked, so pay close attention to your surroundings.