On sunny days and grey ones too in Paris, climb the spiral steel staircase up to this open air rooftop bar.
From here you can see the Paris rooftops of the surrounding Belleville area, they're typical Paris and not typical Paris too. You can even see all the way out to the Sacre Coeur on the hill in Montmartre.
They have a restaurant on the next level down too that's supposed to be amazing. On amazing summer days you may have to wait in the line down on the street but it's always worth it to come up here.