Excelent location, close to everthing (metrô, Gran via, Puerta del Sol, Royal Palace, Plaza maior, Parque do Retiro, Museus) but the apartament is very quiet.
Its a 4th floor in an old building without elevator, the apartament is simple but with everthing we need and the bathroom is reaaally smaall!
If you are OK with that, its a really nice place to stay.
I would stay there again!