Carlo is an excellent host who knows the area quite well. You would do well to ask him for some suggestions regarding what to see and what to do.
The apartment is in an excellent location! It's literally less than a minute until you reach the busy and lively streets that is Madrid. Close to shops, sites and sounds. The apartment however, is still peaceful and you will not hear people or the traffic at all. I had a peaceful night sleep for the 2 nights I stayed there.
The overall apartment itself is very clean and spacious. Carlo likes to keep it keep things clean and tidy. This goes for the bedroom which is very spacious and the bed is large and very comfortable.
I would definitely coming back here next time Im in Madrid.