We had a very good stay overall. Carlos is very reactive so the communication was great.
The apartment is pretty well located in Madrid, with a metro station nearby, and the city centre is easily reachable walking about 20 minutes. It is also well equipped. The bed and pillows were very good.
The air conditioning makes some noise and the towels were not great. We were also very surprised by how noisy the garbage trucks are in the street below everyday between midnight and 1am. This is obviously not Carlos' fault but it can be annoying if your sleep is light.