Retired archaeologist Victoria Atkins holds in her hands a necklace made from dried juniper berries, thought to bring tranquillity to the wearer and protection from bad spirits.

"It's a ghost necklace," she says before introducing our group of three dozen people to a pit house from 600 A.D., the oldest and first ruin on our 700-Year Tour at southwest Colorado's Mesa Verde National Park. "The Puebloan ask us in our hearts for permission to go into these homes and to say thank you when we leave," she explains.

Our fellow travelers, including some from the Netherlands, Denmark, Texas, Florida and Iowa, gently pass around the featherlight beads.

"My ancestors weren't even Vikings yet," quips a young man from Denmark as we try to grasp the era of ancient Puebloans.

Ancestors to Hopi, Ute, Zuni, Navajo and other affiliated Southwestern tribes, they began settling atop mesas that rise above the Mancos Valley about 550 A.D. From the late 1190s to the late 1270s, they began to create villages in the cliffside alcoves. No one can say for sure why they abandoned the area by 1300 — the best guess is long-term drought and crop failures — but they left behind more than 4,500 archaeological sites, including 600 dwellings built into steep cliffs high above canyons.

This legacy places Mesa Verde among America's most significant national parks and one of the world's first United Nations' World Heritage sites. Millions of artifacts have helped scientists piece together how people lived and survived in these early farming communities, relying on corn, beans and squash, along with hunting.

"Corn has been in this area for 4,000 years," Atkins says. "The Hopi people say, 'Corn is life.' "

My husband, Bob, and I arrived the night before after a drive south along the rugged 133-mile Unaweep Tabeguache Scenic Byway that traverses canyons from northwest to southwest Colorado. From the park's visitor center near its entrance, we made the climb up to Chapin and Wetherhill mesas, which rise more than 7,000 feet.

On clear days, you can see to the Four Corners, where Colorado, Arizona, New Mexico and Utah converge. Haze from lightning-sparked wildfires, though, veiled the horizon as we checked into Far View Lodge. Nearby, wild horses grazed on the hill, tails twitching, mouths munching as evening ebbed into night. A nocturnal chorus of insects contrasted with the quiet of daytime, when only the squawk of a crow or raven rose from the sparse landscape of gnarled junipers and pinyon pines.

The landscape makes resources seem as scarce as shade. Visitor center and museum exhibits prove otherwise. They showed the artistry and ingenuity of early inhabitants who twisted yucca fibers into sandals and fashioned fabrics and blankets from yucca and domesticated turkey feathers for warmth. They wove intricate baskets and made pottery to carry and store food and cook meals. They collected water from cliffside seeps, and used antlers and bones to help dig, plant and harvest crops.

Nothing, though, compares to the skill of early engineers who envisioned cliffside dwellings and carved out villages built for up to 150 people thousands of feet from the canyon floor.

Our tour group eagerly disembarks at an overlook to see Cliff Palace. Our eyes adjust to the curves of the distant rock wall, seeking telltale shadows and shapes.

"There!" I nudge Bob, and excitedly pass over our camera, which doubles as binoculars. Murmurs ripple through our group as others catch sight of brick towers and windowed rooms — like a perfect sand castle — for the first time.

Exploring the cliffs

Our bus follows the six-mile Chapin Mesa loop to reach Cliff Palace. Like Mesa Verde's other cliff dwellings, it can be seen up close only through seasonal ranger tours.

Park ranger Roland Whitted, with a braid in his dark hair and a sprig of juniper tucked behind his badge, helps us snake down a series of narrow staircases until we can turn the corner and enter the ancient palace. No longer looking miniature, buff- colored buildings of brick and stone, circular and square, rise beneath the 60-foot ceiling. It reaches 90 feet deep into the cliff and stretches more than 215 feet end to end.

For almost a century, its inhabitants scrambled up and down using foot- and handholds to reach mesa-top farm fields and to welcome visitors. Whitted gathers us around a circular kiva and points out how tiny the corn cobs used to be by showing us a few — just 4 or 5 inches long — that are preserved in a wall. He encourages us to look up into a tower, impressively built in primitive times.

Before we leave, he leads us in a round of "Happy Birthday" for a girl from Iowa celebrating her 10th birthday, and my husband, who is celebrating 54 years. It seems incongruous yet comforting. Even living half a century feels like a mere blip in time when you're standing in a city from the 1200s.

As we reluctantly leave and begin the climb up the cliff using rustic ladders, we follow Atkins' earlier advice and say a silent thank-you to those who built this magnificent place.

Lisa Meyers McClintick ( wrote "Day Trips From the Twin Cities" and "The Dakotas Off the Beaten Path."