There's nowhere better than Guillaume's home. It is minutes away from Gran Via, the main shopping district of Madrid. He was so nice to allow late check-outs, a major plus point for us as our flight was in the late evening and we did not have to lug of luggages around. The apartment was really clean (we are asians and are super particular about cleanliness of the floor) and is fully equipped with whatever you need for a comfortable stay. We managed to cook brunch on one of the lazy afternoons. They gave us a super wide list of restaurant suggestions as well. :) There's an supermarket that closes at midnight and food market 1 minute away where you can get fresh foods! All in all, we really loved the apartment and were so reluctant to head back to Paris!