With more than 5,000 archaeological sites, Mesa Verde National Park is the largest archaeological preserve in the United States. Among the sites are some of the largest cliff dwellings in the world, as well as mesa-top pueblos, pit houses, and kivas (subterranean rooms used for meetings and religious ceremonies) -- all of which were built by the ancestral Puebloans (also called the Anasazi). The sites here tell the story of a 750-year period (A.D. 550-1300) during which these people shifted from a seminomadic hunter-gatherer lifestyle to a largely agrarian way of life centered on large communities in cliff dwellings.

Mesa Verde must have looked inviting to the ancestral Puebloans, whose descendants are such modern Pueblo tribes as the Hopi, Zuni, and Acoma. On the mesa's north side, 2,000-foot-high cliffs form a natural barrier to invaders. The mesa slopes gently to the south, and erosion has carved numerous canyons, most of which receive abundant sunlight and have natural overhangs for shelter.

The ancestral Puebloans became adept at surviving here. The mesa tops were covered with loess, a red, windblown soil good for farming. And although water was scarce, it could seep into the sandstone overhangs where the people eventually made their homes. For food, they farmed beans, corn, and squash; raised turkeys; foraged in the pinyon-juniper woodland; and hunted for game such as cottontail rabbits and deer. They wove sandals and clothing from yucca fibers and traded for precious stones and shells, which they used to make jewelry.

To the visitor today, their most impressive accomplishments are the multistory cliff dwellings, which were largely unknown until ranchers Charlie Mason and Richard Wetherill chanced upon them in 1888. Looting of artifacts followed their discovery until a Denver newspaper reporter's stories aroused national interest in protecting them. In 1906, the 52,000-acre site was declared a national park, the only U.S. national park devoted entirely to the works of humans.

The Cliff Palace, the park's largest and best-known site, is a four-story apartment complex with stepped-back roofs forming courtyards for the dwellings above. Accessible by guided tour only, it is approached by a quarter-mile downhill path. Its towers, walls, and kivas are all set back beneath the rim of a cliff. Another ranger-led tour takes visitors up a 32-foot ladder to explore the interior of Balcony House. Each of these tours runs only in summer and early fall.

Two other important sites -- Step House and Long House, both on Wetherill Mesa -- are open to visitors in summer only. Rangers lead tours to Spruce Tree House, a major cliff-dwelling complex, only in winter, when other park facilities are closed; during the summer, you can see Spruce Tree House on your own.

For reasons not yet understood, although possibly related to climate change, these cliff homes were fully occupied for only about a century; their residents left around 1300.

Although Mesa Verde is the largest and probably the most impressive archaeological site in the Four Corners region, it is not the only one. In fact, archaeologists say that from about 700 to 1,000 years ago, this area teemed with busy communities. Following the discussion of Mesa Verde is a quick look at a few of the other important archaeological attractions in the region.

What's in a Name?

The prehistoric inhabitants of the ancient villages of the Four Corners region have long been known as the Anasazi. That word is being phased out, however, in favor of the term "ancestral Puebloans," because modern American Indians who trace their roots to the ancestral Puebloans consider the word Anasazi demeaning. Anasazi is a Navajo word that means, at least according to some sources, "enemy of my people" (the Navajos considered the ancestral Puebloans their enemies). Some are also using the term "ancient Pueblo people."