The Rashidun Caliphate's Remains of Taq-i Kisra wikipedia commons Throughout history much of the world has been ruled by empires.

To be considered an empire an expanse of land must be politically led by either a monarch, an emperor, or be an oligarchy.

As the decline of the U.S. is being hailed in the news and opinion of the world, we thought it would be interesting to look at the biggest empires of the past.

Aside from their leadership model, the only other thing they all have in common is that each of them disappeared.