What geographic feature allowed ancient Greek city-states to remain relatively safe from invasion?

The correct answer highlights the significance of mountains and islands in shaping the safety of ancient Greek city-states. The rugged terrain of Greece, characterized by its mountainous regions and numerous islands, created natural barriers that offered protection against potential invasions.

Mountains served as formidable obstacles for large armies, hindering their movements and making it difficult for invaders to penetrate deep into the territory of the city-states. Additionally, the islands provided strategic advantages for defense, as they could serve as buffer zones and retreat points for the inhabitants. This geographical layout encouraged the development of independent city-states, each of which could effectively protect itself from external threats due to the natural barriers.

In contrast, deserts would not have had a similar protective effect, as they are often inhospitable and would not support the same level of civilization or military organization. Flat plains could facilitate easier movement for invading forces, making it more challenging for city-states to defend themselves. Rivers, while useful for trade and agriculture, do not offer the same sort of natural defense provided by mountains and islands, and they can often be crossed more readily by invaders. Thus, the combination of mountains and islands played a crucial role in securing the autonomy and safety of ancient Greek city-states.