My friend and I initially stayed at this apartment for 4 days and a further 2 days after we came back from Meteora. It is located in a very pleasant part of Athens and yet only a couple of metro stops from the city centre. It is about 2 min walk from Petralona station and just across the street is a large supermarket.
Konstantina met us when we arrived and she ensured that the place is immaculately clean and tidy. She also gave us a number of restaurant recommendations near Petralona and all of them very superb and the food very reasonably priced.
I strongly recommend this apartment and would definitely stay here again if I were to visit Athens again.