It was a great stay. The apartment was free before check in time, so we were able to place our stuff inside the apartment. It was clean, comfortable, had all the necessary things (towels, body shampoo, hair dryer, plates etc)
The location is also very good, it is walkable by foot to all the attractions and the area has many chill pubs.
It also fit perfectly fine for 4 ppl, I just wish we were provided with another key since we only had 1 key.
I would suggest placing a map of Madrid and some other brochures of the city to be able to go around in the beginning.
This apartment is definitely recommended.