I stayed at Sergio's beautiful flat with 2 others and we had a great time! It's a great location, just a 10 minute walk to el mercado de San Miguel and la Plaza Mayor. The apartment itself is quaint but comfortable, which we found very agreeable. Sergio is a wonderful host, always happy to answer our questions, give us advice about the city and offered to meet us for drinks one night. Next time I'm in Madrid I'll definitely stay here again!