I had a fantastic time in Andres' Apartment.
He was waiting for me when I arrived, he gave me lots of hints about restaurants and interesting locations. The apartment is spotless. WiFi works really well.
The location can't be better. The apartment is inserted in the old Madrid area, very quiet but two blocks away from the Teatro Real and 4 from the San Miguel Market.
You have access to everything within short walking distance. I think that the longest walk was to the Reina Sofia Museum, 20 minutes.
He has a full shelf full of books and leaflets about Madrid to help to move around Madrid.
I highly recommend Andres' apartment and I hope to come back to it some time soon