The apartment is not far from the city center, so we didn't have to buy metro tickets.
Fornitures were new and well working, the apartment itself was very clean!
Marina was extremely kind to us, she gave us a lot of suggestions so as to make our stay in Madrid definitely lovely!
The only negative points are two:
1- the apartment is quite hot, but there is a good air conditioner, even if we didn't want to keep it working for long periods
2- the space is quite small for two people
Despite this, we enjoyed very much our journey, we would come back to Marina's apartment!