Question

Which geographic features might have kept the greek city states from uniting?

Answer 1

The Greek  Peninsula is very mountaneous, which means that many valleys, which are good places for city states to arise, were separated from other ones by mountains: this made them easier to defend and harder to conquer.

There are also many islands, which again, are easy to defend and hard to conquer.

So the geographic features are mountains, valleys, peninsulas, and islands