Thank you for everything, Toni&Stathis :)
The apartment was amazing, bed extra confortable, perfect location, only 2 minutes walk to metro station (and only 2 stops to Monastiraki) and across the street of a big supermarket.
If we come again to Athens, for sure we will choose again the same apartment, not only for its location and confortness, but also for the communication with the host, who offered good tips about the city.
Thank you again! :)