The Parisian sewers are, in their way, one of the enduring legacies of Napoleon III, who is Josephine's direct descendant and not Napoleon Bonaparte's. (Bref, Josephine's daughter, Hortense, married one of Napoleon's numerous brothers. Hortense's son became Napoleon III when Napoleon's son with his second wife, Marie Louise, the niece of Marie-Antoinette, died very young.)
Still, like his uncle, Napoleon III loved Paris and saw its glory as a reflection of his own. Therefore, there came Haussmann, widening the streets so that no one could pry the paving stones loose and build barricades again, the gilded Baroque-Era-ate-a-bit-of-romanticism-and-then-vomited-forth-a-building Opera Garnier and the sewer septic system that so fascinated Victor Hugo. It is, in fact, extremely important to have seperate pipes for drinking water and waste products. This became extremely clear after the 1832 influx of cholera, the (hated) government's powerlessness against it, and the resultant revolts. Ergo, Napoleon III decided that, though Napoleon I had introduced covered sewers (then a very innovative idea), it was probably a pretty bad idea for said covered sewers to dump everything in the Seine, and the complex warren of today's Parisian sewers had its birth.
It was such a technological marvel that visitors to Paris would flock below the newly enlarged streets to take a boat ride through the sewers.
Though one can no longer catch a very Romantic skin disease while making the Grand Tour, one can now visit the Paris Sewer Museum and discover that the Parisian sewer rats have only one natural predator, the pet turtles regular Parisians flush down their toilets. Apparently, there used to be an alligator in the sewers to eat the rats as well, but the alligator has since been captured and put into an aquarium in England. The Amateur Historian is not entirely sure why, but supposes it was because the turtles simply couldn't keep up with the competition.
However, the Musée des égouts de Paris has a sign nearby that reads, "Je bois de l'eau de Paris!", which is "I drink the waters of Paris!"
The Amateur Historian now knows that the drinking water of Paris is piped in directly from a mountain stream to the north, albeit in pipes first laid down in the latter half of the nineteenth century, but is still tempted to rip of Descartes: "Je bois de l'eau de Paris, donc, j'ai de choléra!", or, "I drink the waters of Paris, therefore, I have cholera."