There are a vast numbers of differences between the two ancient City States, and also between the two modern cities.
As a quick overview:
- The two ancient cities flourished at different times in history
- Rome ruled an enormous empire whereas Athens was far more limited in size
- Athens inspired great architecture and literature and Rome copied much of it
- Rome was in (what is now) Italy, and Athens was in (what is now) Greece
- Rome lasted much more longer than Athens