Even for non-soccer fans, Manchester United, the team that plays here, is a familiar name. Not surprisingly football/soccer will be played here during the Olympics.
Sounds weird, but this store has the best rooftop terrace with tremendous views of Paris; right next to Opera. And, there's food up there. Just ride the escalators all the way to the top.
Make sure to walk over to the Ile-St. Louis which is connected to the island where Notre Dame is by a footbridge. Less tourists, better place to grab a bite or ice cream (see Berthillon) and a cool neighborhood.