Cinzia was very kind and helpful ! She is a perfect host ! She offered to pick us up at the airport Fiumicino with her own car (against 20€ but it costs 48€ by taxi and 16€ by train). More, she advised us and gave us a lot of lovely and typical adresses in Rome, specially nice restaurants away from tourists !
The appartment is good enough for a couple. The neighborhood is calm. It is close to Vatican but not really close to the famous places in Rome (Trevi, Pantheon, Coliseum, etc.). You can go easily to Vatican by walking.
But if you don't like to walk, you'll need to take the bus (line 64) at the station San Pietro to go in the center of Rome.
We really want to thank Cinzia, our stay in Rome was perfect thanks to her advice.