Great apartment at the right location between the City Center and Atocha Station (buses from airport all the time). It fits for a 4 people family (two rooms) and both well equipped and calm.
We have really appreciated the interaction with Marta, whom helped us a lot to locate good restaurants (and even booked for us 😀) during this X-mass period when the city gets crowded.
I strongly recommend this apartment and shall definitely contact Marta for our next trip to Madrid.