GREAT location! This place is steps away from everything! It is managed by a company that runs many apartments in the building. The check-in is by using an app that worked very well. Our apartment was number 23 which opens to the 2nd floor on the street side of the building, so could be noisy at night. Kitchen is basic but fine for light meals.
FYI: there is a small elevator ( we had to close the stroller to get in and out).
All in all, good place to sleep in the heart of Madrid!