What Greek city-state was governed by an oligarchy?

many Greek city states were under a oligarchy but they always changed there "government system"

The Greeks had a lot of different kinds of governments, because there were many different city-states in ancient Greece, and they each had their own government. In addition, people's ideas about what made a good government changed over time. Aristotle divided Greek governments into monarchies, oligarchies, tyrannies and democracies, and most historians still use these same divisions. For the most part, Greece began by having monarchies, then oligarchies, then tyrannies and then democracies, but at each period there were plenty of city-states using a different system, and there were many which never did become democracies or tyrannies at all.