I would recommend a 3 hour bike tour from Bike About Tours. http://www.bikeabouttours.com/ Ive been to Paris a few times, and definitely saw more and learned more about the city in those short 3 hours than I did the rest of my times in Paris! The guides are great, personable, and know so much about Paris, one great thing is that they skip all the "main attractions" and focus on places and neighborhoods that you might not easily find on your own! It's well worth it, and SO much fun! Enjoy your time, Paris is such a lovely city!