Konstantinos is a very nice host: uncomplicated, kind, helpful and friendly. He always answered my questions fast and even gave us some advice on what to do in Athens.
The apartment is beautiful and big enough for four persons. We appreciated the air conditioning very much and liked cooking in the kitchen. We enjoyed walking around on the very near "Hill of the Muses" which is untouristic and gives you a nice view on the Acropolis which is on the next hill, and a nice view all over Athens.
The apartment is not completely in the center of the city but nearby and there are metro stations in walking distance.
All in all, we very much enjoyed our stay, and can recommend the apartment, and Konstantinos as a host.