Don't worry, Buttercup! I understand! In the Bay Area, people put up slacklines and hammocks between trees frequently (I recently got a Bear Butt hammock which you can put up and take down in about five minutes, perhaps quickly enough to evade the gendarmes?) and it's no problem. Generally, the people who do so do it respectfully, trying not to overstress the trees. Still, in Paris, I would guess that your best bet would be parks that are out of the way and a bit more eccentric - maybe Parc des Buttes Chaumont? It's wilder and has lots of less-traveled regions, and the park-goers are a lot like the park, less fussy and a bit more offbeat - it's no fastidiously groomed and sign-posted Jardin de Luxembourg or Tuileries, and I love it for that reason. As for everyone else's questions, my hammock weighs a couple of pounds and fits in the palms of my hands (hammock in one, straps in the other). It's not hard to pack for a trip. It also uses softer and wider straps instead of thin rope, which makes it a bit easier on the trees. There's a lot of information out there about people who do long thru-hikes, such as the Appalachian trail, sleeping in hammocks instead of tents. And on warm, lazy afternoons, you can't beat kicking back and reading in a hammock. Happy travels!