You are taking a trip to Greece and yet you do not know where you are going.. This sounds like taking a trip to USA, without specifying the city you are going to visit.
Greece is not as large as USA but it has a lot of places to visit. Athens is a must for a newcomer but then it can only be good enough for a few days. Learn and decide where you are going and then ask here again for specific places. Pointless to start listing names and places.
Unbelievable question .
Start doing basic research on-line , look at vids on You-Tube , read Wikipedia articles , look at the pics and vids on Google-earth . Visit your Library and ask the lady there for a basic guidebook , or buy one from a bookshop .
It depends where abouts in Greece your going? Greece is beautiful and the people are the most friendliest ever
You can eat chicken!
