Most visitors venture to the Marais for two things: falafel and shopping. I go for the gelato.
Unlike the majority of Italian ice cream shops who brandish their mountainous flavors in the windows to entice passersby, Pozzetto (Italian owned and run) stores their ice cream in wells which allows for precise temperature and texture control. The menu never exceeds 12 flavors (all-natural, prepared daily) which means you're guaranteed the highest quality scoops possible.
If, like me, you enjoy an espresso with your dessert, head inside their shop - they have some of the finest brews in town.
When I was living in Paris, one of my favorite nights of the year was the Fête de la Musique, held on June 21 every year. It's a (free!) 24-hour party all over the city to celebrate the world of music. There's a concert for every type of music out there-from orchestra concerts in centuries-old churches to famous pop star performances in parks. If you're a musician yourself, stake out an empty corner and start jamming. Or just roam the streets of the Marais and find impromptu DJ-parties above gelaterias like I did one year. Drinking in the streets in Paris isn't that serious, and this night is no exception- so bring your bottles of vin and start dancing the night away. (Bonus: the metro runs free all night!)