I spent two months in Madrid for work and the Teresa's studio was perfect for me.
1) Good location, close to Retiro park, very well connected by buses and metro (in 4' you are at Atocha station and in less that 20' minutes you are in the city center).
2) The building and the neighborhood are very quite and you can sleep quietly even with the windows opened.
3) Well equipped, with a clean washing machine, fridge, air conditioner, and everything you need for leaving for a long period.
4) Last but not least, Teresa was very kind and answered very quickly to all my requests.
I strongly recommend this studio if you need to stay in Madrid for a temporary long period.