This is a great apartment. It is exactly as described in the details and couldn't be closer to the museums and art galleries. We even went back to the Prado during the free hours in the evening, although there is a big queue, to see things that we missed on our first visit. We had a guide on the first visit which was a really good investment.
Don't miss a trip to the gardens as well. The city tour bus leaves from the end of the street and is a good way to get orientated after you have spent a bit of time gazing at the vertical garden just outside the apartment door.
There is a great little supermarket and greengrocer at the top of the street for basic supplies.
Diego and Eliana were really helpful and organised our transfers to and from the airport for us, which saved us stress and time. They really were at the end of the phone for anything that we needed.
There are a few books to pass the time as well as the TV and good Wifi.
I can't recommend this apartment highly enough. We have been going away as a group for 13 years and 20+ places and decided it was the best ever.