It hosts nearly 5 million tourists a year, but visitors see only a tiny fraction of the Grand Canyon's beauty. Even scientists know precious little about the canyon's 91 mammal species and more than 350 types of birds, its vegetation, and how and when it was formed. National Geographic joins a rare scientific expedition to explore the canyon's entire 277-mile length to unlock some of the mysteries of this wonder of the world.
- Producer: National Geographic canyon evolved? humpback chubb fish rare species road to being extinct?endangered condor redwall cavern glen canyon dam palisades creek kivas cataclysmic water events 11 tribes lived there how long?