We had a great experience at Cristina's and Gustavo's place. Small but cozy and charming, the apartment is very well located on a major thoroughfare, across the street from the Metro and Atocha Renfe train station, within a short walk to Prado and other museums, and many good places to eat.
Despite being on a busy street, it is an AMAZINGLY quiet place because it faces away from the street towards the back edge of Retiro Garden. Nice, clean, well equipped kitchen; pretty terrace with great view, small clean bathroom, and a homey studio room with a loft, full of bookshelves with lots of good Spanish and English books and the host's family pictures and memorabilia. Comfy bed in the loft, and nice couch for two in the studio with lots of pillows and nice clean sheets and towels. Very private. It felt like our own and our friends' homes.
During our stay a radiator in the kitchen sprung a leak and flooded the floor; we called and Gustavo and Cristina came immediately to arrange a plumber and offered to find us a different airbnb so we were not inconvenienced. We loved the place and declined changing apartments. Next morning the plumber came on time and fixed it really fast and well. We were very glad we stayed.
Overall - Cristina and Gustavo were great hosts; they gave us suggestions where to eat and good directions to get around and responded fast to the water leak. It was a really good rental at a good value. We would go back there anytime and would highly recommend it to our friends.