The flat is really nice and well located. Silmara is a really kind person, she agreed with our unconventional check in/out time without any problems.
Two additional remarks:
1) The flat is on a main road of Madrid and has a big not well isolated window on it. Even if it is a pedestrian one during the night it can be really noisy.
2) The bed is a loft bed and the ladder is quite steep and someone could have problems climbing it.
All in all it is a good flat in a good position and we can really recommend it.