Colorado's eastern expanses are part of the High Plains section of the Great Plains. On their western edge the plains give way to the Rocky Mountains, which run north-south through central Colorado. The mountains are divided into several ranges that make up two generally parallel belts, with the Front Range and a portion of the Sangre de Cristo Mts. on the east and the Park Range, Sawatch Mts., and San Juan Mts. on the west. Mt. Elbert (14,433 ft/4,399 m) is the highest peak in the U.S. Rocky Mts. The mountain ranges are separated by high valleys and basins called parks. These include North Park, Middle Park, South Park, Estes Park, and San Luis Park. The Continental Divide runs north-south along the Rocky Mts. in Colorado.
One of the most scenic states in the country, Colorado has recreational parks including Rocky Mountain National Park, Black Canyon of the Gunnison National Park with its narrow gorge cut by the Gunnison River, Dinosaur National Monument in NW Colorado, and Great Sand Dunes National Monument and Preserve in S central Colorado. Mesa Verde National Park and Canyons of the Ancients and Chimney Rock national monuments, once home to Ancestral Pueblo peoples (see cliff dwellers), are in the southwestern corner of the state, a beautiful but formidable area of mesas and canyons.
Most of W Colorado is occupied by the Colorado Plateau, where deep canyons have been formed by the action of the Colorado, Gunnison, and other rivers. Colorado has a mean elevation of c.6,800 ft (2,070 m) and has 51 of the 80 peaks in North America over 14,000 ft (4,267 m) high, thus laying claim to the name "top of the world."
A broad timber belt, largely coniferous and mostly within national forest reserves, covers large sections of the mountains. The mighty Colorado River originates in Rocky Mountain National Park, and the headwaters of the North Platte, South Platte, Arkansas, and Rio Grande also gather in Colorado's mountains. The average annual rainfall in Colorado is only 16.6 in. (42.2 cm), but the state has been able to develop otherwise unusable land and ranks high among the states in irrigated acres. The Colorado–Big Thompson project and the Fryingpan-Arkansas project are two major water-diversion systems that carry water by tunnel across the Continental Divide to farms on the plains of E Colorado.
Most of the population lives in cities among the Front Range foothills, principally in Denver, the capital, largest city, and regional metropolis. Other major cities are Colorado Springs, Aurora, Lakewood, and Pueblo.