Which geographic feature served as a barrier to political unity and encouraged the rise independent city states in ancient greece

I believe the answer is: the mountains, specifically the Pindus Mountains, a range of Dinaric Alps that stretch South from Albania and Macedonia.

The existence of these mountain, made it really hard for outsiders to come and visit greece in both political purpose or trading purpose.

Because of this, it is extremely hard to develop a mutually beneficial foreign relation with greece, which encouraged the rise independent city states

the geographical feature that served as a barrier to political unity and essentially created the Greek city stated was the mountains, specifically the Pindus Mountains, a range of Dinaric Alps that stretch South from Albania and Macedonia.