Karen's place is exactly as described and the location of the accommodation is perfect for exploring Madrid with all major attractions within walking distance. Atocha Station is also <10 min away by walk.
The lane Casa Isabel is nice and quiet and is dotted with a few very good restaurants which are worth trying.
Karen is a wonderful host, very friendly and welcoming and all communication from her side was clear.
The apartment is neat, clean and tidy with all necessary amenities.
Would definitely recommend a stay here for a solo traveller wishing to explore Madrid.