Appartment is in a great location. Perfect for exploring and lots of public transport available.
Air-conditioning works great however be aware the unit is only in the living room so the bedroom will be less cool.
Because of its locations (in the back of the house on the ground floor) the appartment gets pretty humid at times. This goes away when the air-conditioning is running.
Generally the apartment looks like the pictures but is a little bit more used (to be expected because it is not brand new) and darker but this is an advantage since it doesn't heat up too much.
Overall I would recommend this place to stay for a few days in Madrid.