I booked this apartment for 12 people. The place is near to the center, you need not to buy the transport ticket if you want to visit the most important things (like the Prado Museum) and it is very clean like an Hotel. Mar has been a nice and available host. When we arrived She waited us home and gave us a lot of good advices and she were helpful during all the stay. The apartment is spacious and has all the things you need for your stay. Even if it was August we didn't suffer the heat. The neighborhood is silent and it is near to supermarkets and shops.
The best apartment and host so far! Totally recommended ;)