My friend and I had a fantastic holiday staying in Cosy Callao. The apartment was decorated to a very high standard with good appliances in the kitchen for preparing meals and we also loved the shower with its multiple heads! It was very comfortable to spend time in some evenings, and the beds were very comfy. On arrival Vanessa met us at the apartment , and gave good recommendations on things to do and places to eat.
Another positive point about this apartment is its location; it is within walking distance of everything in central Madrid - we didn't use public transport at all! Also the street it's on has a nice buzz about it with lots of wee cafes and restaurants.
Would 100% recommend this as a base from which to explore the city, and would love to stay here again on a future trip to Madrid.