This the perfect place to have a pit-stop in Madrid. The area is unbeatable and the apartment manages to offer a quiet spot in a very lively area.
Juan Sebastian and his wife are super nice, very easy going and responsive. Their dog is very cute and friendly. When you come home, he barks but only because he is excited that someone arrives.
The room is like described, very small and only a bed for one person and no window. You are welcome to use the living room and the kitchen as well as the bathroom are nice and very clean. I wouldn't spend a month in there I guess but for a short stop with you being outside mostly anyway it makes it perfect in regards to price and location.