Mesa Verde National Park preserves the cliff dwellings of the ancestors of the modern Pueblo Indians. There are said to be 4,000 archeological sites within the park boundaries, and many more such ruins throughout the Southwest. We toured the most accessible, Spruce Tree House, in the remnants of the big snow that swept the Rockies this week. Kivas are circular pits, 10 feet deep, cut into the rock and covered by a wooden ceiling and then a carefully fitted mortared stone roof that is level with the plazas that join the buildings in these small villages in the sides of the mesas. Although originally understood by archeologists to be solely for ceremonial uses by the men and boys of the village (sort of frat houses), new evidence suggests broader community uses especially in the colder months when these underground chambers would be the warmest areas available. So perhaps comfort trumped sexism, at least for part of the year. The distinctive pottery dates from about 1250 AD, just before these dwellings were abandoned somewhat abruptly due to a prolonged drought or hostile neighbors (or both). The structures sat for 600 years essentially undisturbed until some cowhands stumbled upon some of them in the late 1800s. Although serious looting reduced them until the Park Service stepped in, they are amazing places to visit, even on a wintry day.