"The hotel is on the Chamartin station that is going under mayor remodelation. The hotel did send the notification about that. It might be noisy during the day, but they stop the work in the late afternoon, so it was much calmer.
On the other hand, rooms are run down, with quite uncomfortable beds, but the biggest problem is that although windows can be opened (still during the day it is quite noisy), there is no air circulating in the rooms, and the AC, even on a hot day like it was when I stayed, was not turned on. I was suffocating in the room when I entered, and I was informed that due to hotel policy, the AC (cold) would only be turned on after May 15. Still, the outside temperature was 27 °C. The wifi in the first room I was assigned was not connecting, but after coming down twice to the reception to complain, I got the new room, with a better connection (but not a better air circulation). Anyway, it is just an OK option if staying for one night. It is well connected with the center of Madrid by metro and suburban train. The station is just 2 min walk from the hotel."