What are some examples of elite groups holding all political power?

I know of different types of governments and ideologies where power is placed in the hands of the privileged and elite, such as oligarchy and meritocracy, but what are some examples of this occurring in history? I know there was the time before the apartheid in South Africa but what of other blatant examples? Does anyone know of any time these systems occurred in the history, or in more modern times, and how these systems impacted the countries or areas in which they were implemented?