We had a wonderful stay at Gabriela's apartment. It was situated in a cozy and lively neighborhood. All the sightseeing points, like plaza mayor, the palace, cathedral and museums, are within walking distance.
The apartment itself is very nice, fully equipped and clean. We loved the spacious terrace, which has a nice view over the city. The bathroom is quite small, but the shower is great. The only thing we missed was some more space / racks to hang towels and clothes.
The communication with Gabriela and her sister Maria was very easy and pleasant.
Definitely recommend this place during a stay in Madrid!