We spent two weeks over Christmas in Ruth's apartment. It was a great experience. The apartment is on a quiet (surprisingly) and pedestrian-only street within 5-minutes walking distance of Plaza Mayor and Palacio Real. It is also 1 minute from the Dias grocery store, fully stocked with breakfast and lunch/dinner foods. Our 7-year-old really enjoyed the largest playground in Centro Madrid next to Plaza de Espana, which is about 10 minutes away. It's also within walking distance of the Prado, Thyssen, Reina Sofia, Teatro Real, Teatro de la Zarzuela￼ , and many other theaters and museums. We highly recommend it if you plan to visit those places.
The interior of the apartment is cozy and well-heated for the winter. It has a fully functional kitchen, washing machine, and shower with excellent water pressure. There is a charming little balcony that looks out to the building’s courtyard.
Ruth is very friendly and allowed us to check in at 8 am.