We had a wonderful stay at grey Matter 1 in Athens.
The location is very close to the centre of Plaka and the Akropolis, which is great if you don’t have that much time to explore Athens. Nevertheless Plaka is very touristic and crowded!
The apartment is quite big and it was easily accessible - though we arrived late at night -, it was very clean and equipped with everything you need (towels, soap, coffee and even a bottle of wine).