Chelo's apartment is the best I ever rented via Airbnb. Location cannot be better - in fact, it's located even better than the King's Palace. :-) Wherever you wander in Madrid: Sol, Plaza Mayor, El Palacio Real, El Prado, El Parque de Buen Retiro - it's never more than 3 - 20 minutes away. If you want to take a day trip, Atocha train station is also very close by.
All amenities are there: a noiseless AC, nice flat TV, visible from the bed, extremely comfortable mattress, strong shower, a fridge, a stove, a teapot. Every detail is thought-through and the apartment is very clean. It's also amazingly quiet, considering the central location.
Communication with Chelo was easy and very pleasant. The check-in and check-out could not be any better.
In other words, all was perfect and I am dreaming of coming again!