We stayed at Carlos' apartment for 5 nights during our trip across Spain.
Carlos himself is a great guy, easy to stay in touch with, accommodating, honest and speaks good English!
It should be noted that the apartment is on the top floor of the building. There is no lift so the stairs can get a little taxing. However, this is also part of the appeal, as you get total seclusion and a wonderful roof top terrace that gets great sun, shade and Carlos' wonderful selection of fresh herbs!
The apartment is perfect for your break and has everything you need for a comfortable stay including great air conditioning. The location is in a perfect spot, 2 mins to metro, 10 mins walk to Atocha station and 20 mins walk to plaza del Sol. Madrid is easy by foot but the proximity of the metro makes it even easier should your feet need a rest. There are numerous bars and shops right outside your door so nothing is an issue.