Faulting and rifting has channelled East Africa's rivers to provide a sanctuary for mighty gatherings of hippos and birds. The same turbulent forces also created the freshwater lakes, thousands of feet deep. Each lake has evolved its own unique species; Lake Malawi alone has more species of fish than any other lake in the world, while above the surface, enormous swirling clouds turn out to contain literally billions of insects, which form the basis for the extraordinary ecosystem. Further north, chemicals leached from the Rift's alkaline volcanoes have created some of Africa's most inhospitable habitats: the caustic soda lakes. Yet even here life continues to flourish as flamingos have adapted to this harsh world and they gather in their tens of thousands. At its northern extremity, the Rift plunges into the sea at Djibouti and enters a world of giant corals and shoals of colourful fish.