We were only in Kristian's apartment for a few nights, but our time there was great. The location is excellent, close to Plaza Mayor and an abundance of eateries and shops. Also well within walking distance of the Prado and all the museums and botanic gardens.
The building was quiet, the bed was comfortable, and the shower was great.
Would recommend this apartment to anyone thinking of visiting Madrid, which is a great and very walkable city :)