If someone offered you a glass of water directly from the Seine, would you drink it?

You might if you had lived during the Middle Ages. This city underneath the city, literally its guts, showcases the history of the sewer in Paris, going all the way back to Roman times. It requires a sense of adventure, since you're going under the city instead of above it.

Waste management was begun minimally during Napoleon's regin. However, Baron Haussmann should have been knighted for developing a system to separate the waste water from the drinking water later in the 1800s. At the time, the network of sewers was mere 360 miles long. Compare that to the present day length of about 1,300 miles long (stretched out, it reach all the way to Istanbul!). You can even see the street number on the pipes that show to which building they belong.

The hourlong tour starts with a film, continues with historical photos and displays (check out the decorated toilet seats) and ends with a walk through the maze of tunnels, guided by an "egoutier" (sewer worker). There is a mild odor (it is a sewer afterall), but the historical value of the the technology more than makes up for it.