Cesar was incredibly responsive by email, and welcomed us upon arrival with keys and great advice about restaurants and entertainment. The apartment was spotless, comfortable, modern and wonderfully located. Las Letras is an atmospheric, historic neighborhood, close to the Prado and Parque de Retiro, with great food and beautiful plazas nearby, yet quiet enough to allow you to sleep well at night. It's only about a 10-minute walk from the Atocha train station. You couldn't find a better spot to stay in Madrid!
The fourth-floor apartment gets plenty of light and a nice breeze, but the bedroom got hot during an unseasonably warm couple of May days. There is central AC in the building, but it's also controlled centrally - the thermostat in the apartment seems mostly to run the fan. There is a separate large moveable "cooling fan," which helped a lot when we put it in the bedroom. I imagine during the summer they probably crank the central AC up higher. Cesar was very helpful and prompt in answering our questions about the cooling system and the washing machine.