We found ourselves in Athens over the Greek Orthodox Easter. It was quite special, especially the fireworks at midnight on Saturday, seen from the balcony. Don't be concerned if you find yourself there at this time.
This flat has everything you need - location, safety, cleanliness. The balcony is terrific with half shade and half sun. The view of the Acropolis at nights is unforgettable. The flat isn't huge, but it has everything you need. Did I mention the balcony?
The management company was expert and very quick to answer any of my queries. I can highly recommend renting from them.
You would be hard pressed to find superior accommodation, IMHO.