Grand Canyon

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?