The flat is very well located, it's close to the rail way station and on the other hand you'll spend not more than 15 min walking on foot to the city center (if you don't like to use subway, which is 3 min walk from the flat))
I liked staying at Carmen's place. The room was very cosy and the bathroom was very clean. Also the host are really great: Carmen's son Nacho was very friendly and helpful.
Muchas gracias por todo y creo que si viajo a Madrid me quedaré en la casa de Carmen otra vez)