4. Shop: Tom Greyhound
The modern design at @TomGreyhound—a Korean concept store recently opened in Paris—runs a close second to the stellar lineup of sought-after fashion labels that it carries: Peter Pilotto, Kenzo, and Thakoon, to name a few. Even if you're not planning to shop, stop in to check out the space's interesting architectural layout. 

Also noted: the Marais' small-scale department store @MerciShopParis has quickly become a Paris institution. Give yourself time to wander the three floors of fashion, beauty, and home decor as well as the shop's used book cafe.