Best croissants and
pain au chocolat
Why locals love it
Simply put, because it makes an excellent and delicious array of baked goods. Outstanding cakes, viennoiseries and little baked treats means that the shop is often busy. They also offer a very reasonable lunch menu, where 7.50 euros will get you a (delicious) sandwich, cold drink, and dessert (take the peach tart!)
Why you should visit it
Okay, it's not at all a 'local secret', but it's well known and recommended for very good reason. If the words 'best croissant and pain au chocolat' aren't enough to sell the place to you, then a. may god have mercy on your soul and b. their chocolate cake "Le Vollon" is pure sex in cake form.
Don't keep pastries in their paper bag. Eat them straight away! Also, terrible coffee.