It's one of America's iconic national parks, best known for its towering granite cliffs and spectacular waterfalls. But even though nearly four million people a year visit Yosemite National Park in California, few have ever seen this remote section of Yosemite hidden deep in the high peaks of the Sierra Nevada Mountains. Greg embarks on a rugged journey into a region of the park few people ever see. The alpine landscape here is breathtaking, and also treacherous. Focus and preparation are key to a safe and successful trip.