"The sun never sets on the British Empire." http://en.wikipedia.org/wiki/File:Richard_Simkin03.jpg History has seen empires that stretch across a fifth of the world; others that ruled hundreds of millions of people; and some that lasted more than a millennium.

Each empire seemed unstoppable for an age, but they all crumbled in the end.

Indeed, the age of empires may have ended with World War II, as world powers have moved on from colonization and conquest in favor of geopolitical and commercial influence.

We've ranked the 19 greatest empires of all time by the number of square miles each had conquered at their peak.

