The communication with Kristian was great from the start, very quick, friendly and precise. The apartment has a great location, in walking distance to the city centre, the lovely Lavapies quarter and more.
Check-in was quick and very friendly, we got some good recommendations for bars and restaurants nearby, too. The apartment was very clean, functional furniture, "Ikea style", again this is meant in a positive way.
The apartment is a in building which also holds a hostal and many more apartments that are being rented out. So it might get lively when people return from their night out. The building and the apartment are not exactly sound-proofed, but that is not an unusual thing in Madrid and Spain. So just go with the flow.
I will surely book that apartment again.