Marianna's studio like flat is a great place to stay if you need a place for one or two people and want some privacy. The apartment is charming with a nice balcony with colorful flowers.
The location is great too but, as the apartment is next to Mount Lycabettus (one of the the attractions in Athens) it's quite a steep walk ascending to the apartment, so it can tiring but that also means you have a great view of the city.
To get to the center (or the tourist spots) you can either take a metro or a 20 to 30 min walk. Which means the place is close enough to the center but far enough where you can go to a few nearby local Greek tavanerias/restaurants that aren't tourist traps (thus good value and quality ).
Overall I had a great stay. Highly recommended.