It's certainly one of the wonders of the natural world. As you stand on the rim of the Grand Canyon, the great gouge out of the earth spanning the state of Arizona, you really feel the power of nature.

The canyon itself is relatively new in geological terms. Formed over the past 30 million years, the force of the Colorado river, driving its way from the Rocky Mountains towards the gulf of California, has carved an immense scar in the surface of the earth.

The river now flows a mile below the rim of the canyon, and the views from the top are spectacular. It's fascinating looking at the layers of the rock in the Canyon, some dating back to the early days of the earth, some 4 billion years old.

The walk along the rim is not for those who suffer from vertigo. Some of the drops ore severe and deadly, but the panorama is immense and the view breathtaking.