We had a great time at Katerina's flat. It is very well located, in the Koukaki neighbourhood (right behind the Acropolis), in a very nice and quiet street.
The flat is on the ground floor and has a nice courtyard.
Also, we were welcomed by Katerina's mother who took special care of us, had left biscuits on the table and food in the fridge and helped us book a taxi.
Katerina was very helpful as well, giving us good addresses on where to go, where to buy nice Greek products, where to eat.