Very nice apartment in an excellent location if you are staying in Madrid for a few days and want to explore the center: short walk to Palacio Real, Plaza Mayor and all the old city streets. Longer (but enjoyable) walk to Prado, Museo Reina Sofía, Thyssen-Bornemisza, El Retiro park, Faro de Moncloa. Metro is very close by, Cercanías (Príncipe Pío) is 15-20 minutes walk. There's a good grocery store close by (Supermercados Dia). Some great restaurants are all around that area.
The apartment is in a small street that is quiet. The apartment is small, but is just the right size for one or two people visiting Madrid.