We can probably thank Greece's mountainous and fractured geology for the way in which its culture developed. The many mountains in Greece, in addition to its many islands, created countless natural barriers. This meant that journies that may have been short as the crow flies were long and arduous by land. As such, it was not until the 19th Century that the nation became unified as a single self-ruling country. Throughout much of antiquity, Greece was a series of city-states or polises with separate governments and regional cultural differences.
These different city-states at times got along and made alliances, but also had frequent conflicts, such as the Peloponnesian War between Athens and Sparta. Local regional identities developed as a result of this with variations in which religion was practiced and society was structured. So even though there were commonalities throughout Greece, such as a more or less common language, there were also marked differences between regions separated by mountains (and the sea). It was not until the Roman conquest of Greece in the 2nd Century BCE, that Greece became truly unified under a single political body.
The rocky mountains of Greece also influenced the way agriculture developed. Grains and crops that grow well on hillsides, such as barley, olives, and grapes became staples of the Greek diet. Hillsides are also useful for grazing animals, such as sheep, goats, and cattle. The meat and diary of these animals became, and still are, a significant part of the Greek diet.