The stained glass in the store and the view from t...

The stained glass in the store and the view from the upper floor are wonderful. You should take a peek without shopping.
Even if you don't understand the language, there is also a school-style restaurant where you can put your favorite food on the tray and pay for it.
There are also several restaurants on the rooftop where you can dine while enjoying the view of Paris such as the Opera Garnier.