A small but nice little apartment in one of the best neighborhoods in Madrid.
The building is quite nice, with 24 hour doorman and elevators. The apartment is small, about the size of a hotel room, but more than sufficient for a stay in the city. The location is also great.
My only real problems were the following:
1.) Check-in was quite confusing with irregular communication from Isaac and co. leading up to the day. On the day of, I received no response to my texts until I called. Then I had to go wait at the front door to the apartment for 30 minutes because no one was there.
Definitely plan ahead with them.
2.) This one is very minor, but the chairs on the dining table are all broken and cannot support any weight. This wasn't a problem for me as I never used them, but don't expect to host dinners here.
Overall a very comfortable stay. I would stay again.