Although there's some controversy over its history, it's generally accepted that the Colorado River has been eroding the Canyon's rocks over the last 6 million years and that some of the exposed rocks are nearly 2 million years old which is half the age of the Earth.
A stunning view wherever you are, thrill-a-minute rafting down the river or for the more sedate a visit to one of the two rims, each very different and rarely visited on the same trip. The South Rim is easier to get to and more popular with more services and huge panoramic views. The quieter north rim is 1,000 feet higher than its counterpart and has wildflower meadows and impressively tall stands of spruce and aspen.
Native Americans, who have settlements in the canyon itself and its many caves, have continuously inhabited it.
It is now managed by the Grand Canyon National Park, the Vavasupai Tribe and the Hualapai nation, whose new addition to the landscape, the Skywalk is controversial, different and worth a visit.
Where is it?
In the Colorado Plateau, carved by 225 miles of the Colorado River, part of the Grand Canyon National Park in Arizona USA.
What is it?
A huge, steep-sided fissure that exposes uplifted Proterozoic and Paleozoic strata, some of the oldest rock strata in America. The Grand Canyon is 277 miles (446km) long, up to 18 miles (29km) wide and over 6,000 feet (1,800 m) deep.
Best time to visit?
Between September and November there are fewer tourists, temperatures are between the mid 20s and mid 70s in and there are more facilities and trails open than between March and May, the second best time. June to August is peak season with long sunny days and a temperature between 40 and 85 degrees centigrade. This is dangerous as canyon breezes can disguise the sun's rays, so you might not know that you're burning. A hat and sunscreen is vital whatever the season.
Yavapai Observation Station at Yavapai Point is well worth the hike. It has incredible panoramic views and is often described as the best ways to see the Colorado River and Phantom Ranch. If you're unable to do that, take the two hour Grand Canyon Steam Railway, which shows both the South Rim and the area's history, including historic train depots that look nearly the same as they did in the 1900s.