The Grand Canyon in Arizona is one of the largest and most beautiful of all canyons. It extends 450 kilometers.

The surrounding area does not make you suspect the existence of such a great opening in the earth. You come upon the canyon suddenly when you reach its edge.

Then you are looking at a land like nothing else in the world.

On the other side, sunshine lights up the naked rock walls in red, orange, and gold.

The bright colors are the result of minerals in the rocks. Their appearance changes endlessly -- with the light, the time of year, and the weather. At sunset, when the sun has moved across the sky, the canyon walls give up their fiery reds and golds. They take on quieter colors of blue, purple, and green.

The Grand Canyon has several weather environments. The top is often much different from the bottom. On some winter days, for example, you may find cold winds and snow at the top. But at the bottom, you may find warm winds and flowers.

Some of Earth's oldest rocks are seen here. There are many levels of granite, schist, limestone, and sandstone.

Several kinds of plants and animals are found in the canyon and nowhere else on Earth. Because the canyon's environments are so different, these species did not spread beyond the canyon, or even far within it.

Native American Indians occupied the Grand Canyon 3,000 years ago. Evidence of their existence has been found in more than 2,500 places so far. Bones, hair, feathers, even the remains of plants have been found in deep, dry caves high in the rock walls.

There are several other ways to visit the Grand Canyon. Hundreds of thousands of people see the canyon by air each year. They pay a helicopter or airplane pilot to fly them above and around the canyon.

About 20,000 people a year see the Grand Canyon from the Colorado River itself. They ride boats over the rapid, rocky water. These trips last from one week to three weeks.

Visitors can see the Grand Canyon in still another way. A huge glass walkway, called the Skywalk, extends 21 meters from the edge of the Grand Canyon. The Skywalk is suspended more than 1,200 meters above the bottom of the canyon. It is shaped like a giant horseshoe. Visitors pay 25 dollars each to walk beyond the canyon walls, surrounded by the canyon, while standing at the edge of the glass bridge.