What is the largest city in ancient Greece?

The ancient Greek world was comprised of a couple of thousand independent city-states stretching from Spain to Asia Minor. So there was no 'Greece' or capital of Greece - the Greeks were a people not a nation as in today's term. There were major cities such as Thebes, Corinth, Athens, Sparta, Syracuse, Miletus, but as there was no country, there was no capital. Each city was the 'capital' or centre of its territory.