We absolutely loved stayed staying at Antonio's apartment! The location is stellar and close to everything. The apartment is clean, updated, and fairly spacious for an apartment in downtown Madrid. Even though the apartment is on the first floor, it situated in the back of the building on side streets, so it is very quiet. Antonio was one of the most communicative hosts I have ever had! He responded at all hours when I was booking from the U.S. and while in Spain.
One thing to note- if you do not have international Wifi, be sure to download the check in instructions via the link Antonio sends you BEFORE you get to the apartment as you won't be able to access the apartment Wifi until you are inside the building. Highly recommend Antonio's place!