Sergio's flat is extremely nice. More than everything, it's perfectly located, the neighborhood is filled with restaurants and bars and nice streets. It's pretty close from the museums (~10 min on foot) and a few minutes from the plaza Mayor and Puerta del Sol. The apartment itself has all that's needed, 3 double beds, 3 bathrooms, a well-furnished kitchen.... It's facing a private court (not the street) so it's really quiet. All in all, we had a great time and really enjoyed our stay. I'd definitely come back when I am visiting Madrid again.