Our family fell in love with Ernesto and Antonio's apartment. Our experience of beautiful and lively Madrid was enhanced because we got to go home to a comfortable and welcoming place right at the heart of Madrid. The balconies in each room were a plus. :) We got to see Madrid from a nice vantage point.
Everything was walking distance - from Plaza Mayor to Mercado de San Miguel to several Metro stations. Nightlife spots and great restaurants are also a few meters away.