One of the great engineering feats in Paris is… the sewer system. Okay, there’s the Eiffel Tower, too. And sure, maybe it’s a bit more majestic, iconic, photogenic, yada yada yada. But the lowly sewer system is a pretty impressive deal in its own humble way. You can even take a tour of a portion of it—and Rick Steves gives it a thumbs up, although I haven’t been able to get the girls interested in it (I have no idea why).
Each day in Paris you’ll find water flowing down the gutters of different streets cleaning away debris (mostly dog poop, of course). And sometimes you’ll catch the pigeons taking advantage of a free bath.