S1, E2: Tour the mightiest mountain ranges, starting with the birth of a mountain at one of the lowest places on Earth and ending at the summit of Everest. One of Earth's rarest phenomena is a lava lake that has been erupting for over 100 years. The same forces built the Simian Mountains where troops of gelada baboons live, nearly a thousand strong. In the Rockies, grizzlies build winter dens inside avalanche-prone slopes. The programme also brings us astounding images of a snow leopard hunting on the Pakistan peaks, a world first.