Breathtaking is right. We will return to Greece and we will definitely stay here. It is so easy to get to. From the airport take train #3 to Athens. At Syntagma station take train #2 one stop south to Acropoli station. When you exit to street level the apartment is in front of you. The Acropolis is on your left and the museum is on your right. In between are a dozen open air restaurants and tavernas and no cars. We landed at 4:30 and saw the sunset from Mars Rock overlooking the Agora. Panos met us when we arrived and marked up a map to show us everywhere to go. (North side of Athens is no-go territory) but we found a great music store there and my musician son bought a Balalaika.
The apartment has great views and the roof is even better. We were quite comfortable with 5 adults. We were very active and walked all day. Three nights was the absolute minimum for this stay. I would recommend at least 4 or 5 nights to see Athens properly. The 5 day metro pass for 10 euros each is a great deal and will get you everywhere except the airport.
I could say more but my best advise is to see everything Panos circles on the map. We only met him when we first arrived but he was so thorough that we didn't need to reach him again. He is an amazing host.