This apartment complex is the best I've ever found in Madrid and it's on one of the best streets in the ideal neighborhood of Salamanca. There are high-end shops, bars, restaurants and you are right next to the Puerta de Alcala and the gorgeous Parque Retiro.
The building is gorgeous and the airbnb itself is modern, clean and has everything one needs, including a small kitchen, washing machine, etc. The building is also incredibly quiet and all of the products (especially the bedding and mattress) are top quality. I have been incredibly comfortable here and happy making it my home for over 30 days.
The staff are super responsive to emails and very helpful. This place is HIGHLY recommended and I will absolutely return.