It's nice to be a time traveler in a city like Athens!
Athens is the oldest and most historic city in Europe. It is not only the city of the ancient philosophers of the classical era, even though its appearance refers directly to Ancient Greece. Literally everyone "passed" through Athens, they have "passed" and left their mark, civilizations that have either "integrated" into the identity of the modern Greek or not.
It would be best to do this tour in the first few days of your stay in Athens, so you can get an overview. I will tell you about everything and you will see almost everything, so you can decide what is really worth doing during your stay.