Ancient Greece was divided into independent city-states due to its mountainous geography. Between the 8th-6th centuries BC, many Greeks migrated and founded colonies around the Mediterranean as the population increased. Two major city-states were Athens and Sparta - Athens was a rich cultural center with the first democracy for free males, while Sparta had a government ruled by a few and was culturally different. Alexander the Great later conquered the Persian Empire and controlled the largest empire in history.