For us its the awesome walkable streets that make this area exciting.
Our number one goto in the 2nd, is without a doubt is Rue Montorgueil (food street), they have the most amazing cheese shop, that has 10euro trays for the uninitiated,(us), the bakeries, (boulangeries are to die for), food just seems to to flow in the street like water, oyster shucking in the open, fresh fruit, excellent value, and the outdoor terracing, we were. Never bored walking up and down this street, or the ones in the list for that matter.
Things to do list:
Passage du Grand-Cerf, covered passage, probably the nicest in Paris.
La Porte Saint-Denis and Rue Saint Denis, awesome cheap clothing shops, and all things fur, also a little seedy, (red light).
Rue Étienne-Marcel, Posh shopping, jewellery.
Rue de la Paix, highend fashion.