How many days to spend in Greece for mythology geeks?

Hi, I am planning to visit Greece for a mythology tour this coming December. But, I am wondering how many days should I spend there? Is one week enough? Which places are a must-see for mythology buffs? I am looking for an itinerary that I can follow if anyone has any suggestions!

I probably have around 2 weeks of holiday, should I do 1 week in Greece and 1 week in Italy for a mythology tour?