Greece's geography enabled Greece to achieve something that no other ancient group of people could have even imagined.
First, Greece's mountainous territory (70%) prohibited Greece from forming into an empire. Instead, Greece formed city states that were separate. By the time of Aristotle, scholars estimate that there were over 1,100 cities. This said, we must not give the impression that the nothing held the Greeks together. Things like language, culture, religion, and the olympic games gave a sense of "Greekness." This enabled the Greeks to compete and cooperate with each other in many areas. The outcome was a flourishing of society. Within in this matrix, the Greeks experimented and invented many things, such as democracy.
Second, another geographic quality of the Greeks is that they took to the sea. In fact, almost every polis was 25 miles from the sea. Even the Spartans, who did not like the sea were less than 20 miles away. This fact enabled the Greeks to travel and explore. Through their oversea colonies, they began to spread hellenism, and they were incredibly successful. Had their land been far richer in resources, they would not have taken to the sea, and this would have altered history.
In conclusion, geography shapes a people.
Geography is extremely important to the development of Greek society. I would say that the most important components are the fact that Greece is split into small, manageable regions by mountains and its climate.
The mountains helped develop the political system of Greece. Because it divided the entire, large country into smaller regions, the idea of city-states was created. Overall, it played a massive role in the functioning of the government. Moreover, it helped create an economy. Although the mountains would have made it difficult to trade, it helped shape Greece's economy to what it was.
Also, the climate helped develop Greece's economy. Because the climate is usually mild and rainy, it is excellent for growing a variety of crops, namely grapes. Like I mentioned above, the people from the regions could trade with each other to get what they needed.
Thus, the mountains and climate were important to Greek society.