First-time visitors to Colorado are often awed by the looming wall of the Rocky Mountains, which come into sight from a good 100 miles away, soon after drivers cross the state line from Kansas. East of the Rockies, a 5,000-foot peak is considered high -- yet Colorado has 1,143 mountains above 10,000 feet, including 54 over 14,000 feet! Highest of all is Mount Elbert, at 14,433 feet, southwest of Leadville.

The Rockies were formed some 65 million years ago by pressures that forced hard Precambrian rock to the Earth's surface, breaking through and pushing layers of earlier rock up on end. Then millions of years of erosion eliminated the soft surface material, producing the magnificent Rockies of calendar fame.

An almost-perfect rectangle, Colorado measures some 385 miles east to west and 275 miles north to south. The ridge of the Continental Divide zigzags more or less through the center of the 104,247-square-mile state, eighth largest in the nation.

You can visualize Colorado's basic topography by dividing the state into vertical thirds: The eastern part is plains, the midsection is high mountains, and the western third is mesa.

That's a broad simplification, of course. The central Rockies, though they cover six times the mountain area of Switzerland, are not a single vast highland, but consist of a series of high ranges running roughly north to south. East of the Continental Divide, the primary river systems are the South Platte, Arkansas, and Rio Grande, all flowing toward the Gulf of Mexico. The westward-flowing Colorado River system dominates the western part of the state, with tributary networks including the Gunnison, Dolores, and Yampa-Green rivers. In most cases, these rivers are not broad bodies of water such as the Ohio or Columbia, but streams, heavy with spring and summer snowmelt, that shrink to mere trickles during much of the year under the demands of farm and ranch irrigation. Besides agricultural use, these rivers provide necessary water to wildlife and offer wonderful opportunities for rafting, fishing, and swimming.

The forested mountains are essential in that they retain precious water for the lowlands. Eleven national forests cover 15 million acres of land, with an additional 8 million acres controlled by the Bureau of Land Management, also open for public recreation. Another half-million acres are within national parks, monuments, and recreation areas; and there are more than 40 state parks, including about 10 within an hour's drive of Denver, Boulder, or Colorado Springs.

Colorado's name, Spanish for "red," derives from the state's red soil and rocks. Some of the sandstone agglomerates have become attractions in their own right, such as Red Rocks Amphitheatre west of Denver and the startling Garden of the Gods in Colorado Springs.

Of Colorado's 4.5 million people, some 80% live along the I-25 corridor, where the plains meet the mountains. Denver, the state capital, has a population of well over half a million, with over three million in the metropolitan area. Colorado Springs has the second-largest population, with almost 380,000 residents, followed by Fort Collins (125,000), Pueblo (105,000), and Boulder (100,000). Because of this large, growing population, there is concern that habitat is being diminished by continued development and the needs of so many people.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.