The Great Rift Valley - a vast crack spanning the length of East Africa - is the product of deep-seated geological forces which have spewed out a line of cloud-wreathed volcanoes stretching from Ethiopia to Tanzania. Their peaks provide a refuge for East Africa's most extraordinary wildlife, including newly discovered and never before filmed species which have evolved surprising survival strategies to cope with their challenging mountain environment.

The Great Rift Valley channels a huge diversity of waterways: rivers, lakes, waterfalls, caustic springs and coral seas, spanning from Egypt to Mozambique. Some lake and ocean deeps harbour previously unseen life-forms, while caustic waters challenge life to the extreme. But where volcanic minerals enrich the Great Rift's waterways, they provide the most spectacular concentrations of birds, mammals and fish in all Africa.

The Great Rift Valley provides the stage for an epic battle between trees and grass, its course influenced by volcanic eruptions, landscape, and rainfall. On its outcome rests the fate of Africa's great game herds. In the Rift's savannas, grazers and their predators struggle to outwit each other, forcing one group of primates to develop a social system that paved the way for the evolution of mankind.