This place is awesome! Located just few steps from subway's station in the centre of Madrid (only 15 min. walk to Plaza Mayor or Retiro Park). The building is well-kept. The flat is very clean, quiet and tastefully decorated. The room is small, but it is not a defect. The size is good enough to feel very comfortable and relaxed. Big (king size) bed with excellent mattress, romantic light, a hairdryer, an ac unit, and an iron - all of these stuff help to feel me as I was in 4 or more-stars hotel. What is more in such a hotel you cannot use fully equipped kitchen like here.
And the owner is very kind, helpful and hospitable person.
Don't forget ask him how to open the flat's door. It's not difficult but you must know how to do this.