The area in Paris around the old Palais de Beaux Arts just south of the Seine at 14 Rue Bonaparte is very easy and fun to wander around in for a couple of hours, you can explore various parts of the campus including lecture halls and the amazing library. Wear a light back pack and look like an art student and walk purposefully towards the glass roofed building at the back. If anyone flags you down, say you are looking for the Dubonnet (doo bone ayyy) library and you hope to meet a student there who will show you around. It's a student controlled and creative person dominated space full of art students, but it is a little bit anarchic. (It is between quai Malaquais and the rue Bonaparte, in the heart of Saint-Germain-des-Prés, just across the Seine from the Louvre museum. The old art palais building is generally always open but you wont be able to get into the admin or housing areas. There is a isolated garden there where students bone at lunchtime when weather is good. It's north of the palais. You can see trees at top left. Be polite and friendly and respectful and no one will bother you as you walk around.