7th Arrondissement: Napoléon’s tomb, Musée Rodin, American University, American Library, Eiffel Tower. Boom.
Trip planning is really fun with the Google map feature. Here’s the short URL for this solo day trip, probably on a Monday. Walking from the hotel in the 15 to Napoléon’s tomb and then to the Musée Rodin, stopping at the American University bookstore (as able), Eiffel Tower (via American Library in Paris) and ending at Le Cordon Bleu (Julia child’s alma mater). Less than 10 miles walking tour.