Ancient Greece occupied southern Balkans and western Anatolia. After the 8th century BC, Greek culture expanded throughout the Mediterranean. In the 3rd century BC, Alexander the Great spread Greek influence as far as India. The natural environment of valleys, islands, and seas shaped independent city-states and a maritime economy focused on trade, agriculture, grazing and fishing. Greek history progressed from pre-Hellenic Minoan and Mycenaean civilizations, through a Dark Age after Dorian invasions, then the Archaic age of colonization, Persian Wars, and rise of city-states like Athens and Sparta during the Classical period.