Ancient Greece consisted of a mountainous peninsula and over 2,000 islands in the Mediterranean Sea that lacked good farming land except in Crete. The isolated city-states developed separately, with the advanced Minoan civilization on Crete followed by the seafaring Mycenaeans. Athens and Sparta emerged as the dominant city-states, with Athens developing a direct democracy and Sparta emphasizing its powerful military. The Greeks later fought off the Persians in battles like Marathon and Salamis, then formed the Delian League alliance. Alexander the Great then conquered the Persian Empire and spread Greek culture across his vast new empire before his early death.