My wife and I went to Athens at the begining of June and WOW. ATH is great there is enough to do in 3 days and the flights were not bad but we went out of EWR and got first. Depending on your time frame if Athens is an option go to the islands. Public transit in the city is fantastic and most people speak english plus the food is fantastic. Also my parents got back from BRU 2 weeks ago and loved it there. Good luck.