Gustavo's place is perfectly located for the art enthusiasts. Museum Reina Sofia is a few blocks away and Prado Musuem within comfortable walking distance. The flat looks very clean and all appliances are top quality. So much so that you won't notice the lack of a microwave. It's an IKEA space. Nicely put together, in good condition. The building is more a tenement building than a set of flats and that is probably the main reason there is no natural light, although there is a couple of windows that allows decent ventilation. Also, you will occasionally hear your neighbors going about their daily lives but all in all (and specially late at night) it is super quiet.
Gustavo has put a lot of effort on this place to make it feel like a oasis, an apart world of its own. He will also replay to any of your questions with no delay, in case you have any.