Compare and contrast the sewer museums of Brussels (left hand photos) and Paris (right).
The Brussels sewer museum recently reopened after having been closed for the entire time we had been there, to my eternal chagrin. (They failed to publicize the date of completion of renovations, which is probably wise because they would most likely fail to meet their advertised projections--everything is late here.) Once they took down the big sign announcing the work, we knew they were back in business. Information on the web was pretty scant, but I determined it was open every day but Monday. Not true, actually--it turns out it's open every weekday but Monday, so our trip out there on a Saturday was a bust. We managed to make the best of it, checking out some other stuff in the area and visiting this willow tree that hangs out over the street, its curtain of leaves forming a perfect arch for VW vans to pass underneath.
So it was up to me to check it out on a weekday by myself. Contrast: at the Paris sewer museum, which is open on weekends, the tickets are purchased in an above-ground kiosk and then you immediately descend into the underworld. In Brussels, you enter a beautiful neoclassical temple that faces a matching one across the street and buy your tickets from an actual sewer worker. An exhibit on the undergrounding of the Senne is presented on the ground floor. Contrast: while Paris was ready for their English-speaking fans, Brussels was not. But there were a lot of good pictures and models and memorabilia, so you could fairly easily follow along.
Compare: both felt the need to address the rat question. Paris chose to display their rats frolicking in a forested setting, as if rats are ever found in unpopulated areas. Brussels put theirs in a box with a piece of pipe and a bar of soap or air freshener or something. Both locations allowed you to commune with actual sewers with actual sewage running through them. Brussels included a hand washing station after you had left the dirty areas.
Contrast: unlike the popular Paris attraction, I had the Brussels museum to myself for the entire duration, and I lingered there for longer than I probably would have if there were other people around. Once you got down in the main tunnel, which had a walkway and a railing separating you from the poop-filled Senne, it was a little creepy. Anything could happen down there. I half-wished I was involved in some kind of criminal enterprise and needed to dispose of evidence, because it was the perfect opportunity. Even if they were watching you on cameras from above, they couldn't make it down there in time to stop you from dropping something in the water. Of course, assuming it was a gun or something, it would probably sink right to the bottom, in which case they could dredge it back out. Unless you had planned ahead and somehow made it neutrally buoyant. One should probably experiment in one's own bathtub before undertaking such an endeavor.
Compare: both cities explored water quality challenges in general, although Paris focused on the health of the Seine River whereas Brussels tackled both the local and global situation. Brussels began fully treating their wastewater in...2007. Their first treatment facility came on line in...2000. Shocking yet true. Locally things can only get better. Maybe someday they'll stop using the Senne as a means of wastewater conveyance (yes, that is a photo of the river--contrast it to Paris' Seine on the right) and get rid of the sparsely used boulevards that cover it, returning a bit of pseudo-naturalism to the city. It would be positively enlightened.
Contrast: Brussels' sewers were never the turn of the century tourist attraction that Paris' were.