On my recent visit to Madrid, I stayed at Ramon's apartment for a month. I can assure you that my stay in this place was fantastic not only because of its excellent location close to everything including the subway station, but also because of its new and very safe location.
My apartment was small, but very comfortable, extremely clean and with all the necessary equipment as well as having a small balcony and a super comfortable bed which made my stay more pleasant.
The only thing I lacked was a better internet connection since I work from home and I need a strong and stable internet, but if your intention is to spend more time visiting places and not in the apartment like me, this place is 100% recommended.