A beautiful apartment in stylish Saint-Germain-des-Prés. Footsteps from restaurants and nightlife, and yet secluded enough that you can relax and sleep when needed. Metro is close for any trips out of the neighborhood, but you could easily spend a week never using it.
Yes, you will walk up some stairs to get there. If you have kids, counting the stairs is a good distraction.
Overall, a great way to experience Paris.