Figure out the central idea of this paragraph

In the earliest days of Greece, the country was divided into small, individually governed areas called city-states. City-states were often separated by forests or mountains and were far apart, and the dialects spoken in each city-state varied. Because of these barriers, people did not travel much, so city-states did not frequently interact. If you were born in a particular city-state, you would usually live there your whole life. As a result, each city-state had its own myths that most residents knew and told over and over again.