This was the perfect location for our trip to Madrid! Walking distance to all the best art museums (the Prado, the Reina Sofia, and Thyssen-Bornemisza), as well as to Gran Via, Retiro Park, and Puerta Atocha. There's a Carrefour right around the corner for any groceries you might need.
Another perk – there were several great vegetarian restaurants super close. We especially loved Reineta Vegetariano, a 10 minute walk away, and El Fogón Verde, a 2 minute walk away. (We also availed ourselves of the nearby Burger King, which has a far more extensive veggie menu than they do in the US, and for a much lower price.)
The apartment is very pretty (and well stocked with good books!), the building and street are safe, and communication with the host was extremely easy. I recommend this place very highly. Book your stay here!