At more than 270 miles long, 18 miles wide and almost one mile deep, the Grand Canyon is nothing if not grand. The canyon began forming "only" about six million years ago as the Colorado River cut through the rock on its downward race to the Gulf of California and surrounding Colorado Plateau began to rise upward. Most visitors view the canyon from the various lookout points along the South Rim. The North Rim of the canyon, often closed in winter, is about 1,200 feet higher and much less visited. One item that remains on my list for a future visit is a hike down into the canyon. Although it is a magnificent view from the rim (or a helicopter), it must be even more impressive from the floor looking up.
Not far from the Grand Canyon, and covering an area of 7,500 square miles, is Arizona's Painted Desert, known for the brilliant colors of its landscapes. A few miles to the south is Petrified Forest National Park, which is really more desert, though punctuated with fallen trees from an ancient forest. The trees originally grew in the Triassic Period (240 to 205 million years ago), when the region was a marshland. As they died, the trees were buried by sediment and penetrated by waters rich in silica. Gradually the wood fibers were replaced by silica and other minerals, and the logs were converted to brilliantly colored stone.
To the north of the Grand Canyon, on the border between Arizona and Utah, lies Monument Valley, famous for its large buttes and its role as backdrop in many western movies.
For more information about U.S. National Parks in general, visit the web site of the National Park Service.