For the 8th year, the express road along the Seine River is closed to cars during 1 month (july 20th untill august 20th) and transformed into a great pedestrian way. This is called "Paris Plages" (plages meaning beaches), and as you can see on the picture I took yesterday afternoon, it is quite popular. Not all the express way is like this with sand. You can also find "Cafés", places to play Pétanque, a swiming pool, etc... All of this beeing temporay. I will show more pictures of Paris Plages these next days.
If you want to know more and see some little movies you can go on the Paris website (in English this time !).