If you're craving some outdoor fun, make a day trip to Col du Midi. No walk around the block, this hike is fantastic for some mid-vacation exercise.
You're spoiled for sightseeing choice when in Chamonix-Mont-Blanc. Col du Midi is an ideal place to begin here, but there are many other fine sights to appreciate. Mont Blanc, Aiguille du Midi Cable Car, and Aiguille du Midi are near the steep landmass and will round out your day nicely.