This was a really good stay in Madrid, from Carol and Iván's flat you can walk everywhere! It is located in a neighborhood with plenty of night life and really calm early in the morning.
The apartment was just like the pictures, perfect for a stay of 3 people (originally booked for 4 people but one of us couldn't come for personal reasons, we found that it would be hard to accomodate 4 people since the bed that pulls from under the couch is really small). The only little problem we had was that not all kitchen equipments had european plugs and there was no adaptor available. Otherwise, it was very clean, with all the amenities described in the ad. I really recommend staying at this place when visiting Madrid!