S1, E5: Located near the top of the world, Denali National Park is home to more than six million acres of extreme wilderness. Venture beyond the tourist hotspots and join National Geographic on a low-to-high-altitude trek through Denali's breathtaking ecosystems. Elevation sets the rules in this subarctic land where only the most hardy creatures-- including man-- can survive. Witness remarkable moose-on-moose combat in Denali's taiga forest, follow beautiful dall sheep through the tundra's craggy rocks, and climb alongside an expedition to the death-defying summit of Mount McKinley, North America's tallest mountain. Featuring cinematography of big game, glacier crevasses, and snowcapped mountains, Extreme Alaska: Denali National Park is an absorbing adventure through one of the Earth's most remarkable places.