I was staying in Madrid to attend an art fair as one of the exhibitors and the apartment was just a few minutes walk away from the location of the fair, in the museum district.
The fact that it's situated at street level may alarm you at first, but the spaces are well distributed and I slept well, without ever being disturbed by any kind of noise. It's clean and has all you may need for your stay in Madrid. Plus, the host is friendly and quick to respond and act when needed.