Ancient Greece had a mountainous landscape that divided the people into independent city-states. Two major city-states were Athens, which developed the world's first democracy, and Sparta, which was a strict military state. The Greeks developed advanced thinking through philosophers like Socrates, Plato, and Aristotle. They also fought the Persians and each other in wars that weakened Greece. Subsequently, Alexander the Great conquered much of the known world and spread Greek culture before his early death. The resulting Hellenistic period saw advancements in science, math, and a blending of cultures across Europe and Asia.