[2-1/4 hour documentary] Today, the Songhai Empire is all but forgotten by history. But this medieval kingdom was once the most powerful force in Africa. Find out how this civilization grew up on the fringes of the Sahara Desert, among some of the most extreme conditions that nature can throw at us. Discover how it grew and flourished, passing through a process known as the imperial cycle, and learn about what ultimately caused its sudden and dramatic collapse.