Brilliantly located just behind Reina Sofia and the Atocha Train station. In walking distance of most places, and take a taxi if you want to go as far as Plaza de Espana, you could always walk back and the taxi's can be reasonable if you catch them on the right spot.
This apartment is neat and well set up for the busy traveler to leave their stuff, have a great cup of coffee and a good nights rest in the best bed in Spain.