You have Athens leading the Delian League in a fight against Sparta and their allies, which significantly weakens the city-states. It ends with Athens losing, but all of the city-states have been weakened, and it leaves them open to be conquered by the Macedonians, in particular Philip of Macedonia, and then his son Alexander the Great is able to not just keep control of Greece, of the city-states, but conquer Egypt and Persia and get all the way to modern-day Afghanistan and Pakistan. But after his death, you then have his successors, and Greece falls under the Antigonid dynasty. But eventually, as we get into the second and first century BCEs, it goes under Roman control. And we've talked about this classical period, all of the various contributions. We've talked about the contributions in philosophy from people like Socrates, and Socrates' student Plato, and Plato's student Aristotle. But there are also significant contributions in mathematics.