The landscape northeast of Flagstaff is desolate and windswept, a sparsely populated region carpeted with volcanic ash deposited in the 11th century. It may come as a surprise, then, to learn that this area contains hundreds of archaeological sites. The most impressive are pueblo ruins left by the Sinagua (the name means "without water" in Spanish), who inhabited this area from around 1100 until around 1250. According to contemporary Hopis and Zunis, the people who lived in this area were their ancestors, and it is easy to see the similarity between the stone-walled pueblos here and the traditional homes on the nearby Hopi Reservation. Today the ruins of several ancient villages can be seen in this national monument.

The largest of the pueblos is Wupatki Ruin, in the southeastern part of the monument. Here the Sinagua built a sprawling three-story pueblo containing nearly 100 rooms. They also constructed what is believed to be a ball court, which, although quite different in design from the courts of the Aztec and Maya, suggests that a similar game may have been played in this region. Another circular stone structure just below the main ruins may have been an amphitheater or a dance plaza.

The most unusual feature of Wupatki, however, is a natural phenomenon: a blowhole, which may have been the reason this pueblo was constructed here. A network of small underground tunnels and chambers acts as a giant barometer, blowing air through the blowhole when the underground air is under greater pressure than the outside air. On hot days, cool air rushes out of the blowhole with amazing force.

Several other ruins within the national monument are easily accessible by car. They include Nalakihu, Citadel, and Lomaki, which are the closest to U.S. 89, and Wukoki, near Wupatki. Wukoki Ruin, built atop a huge sandstone boulder, is particularly picturesque. The visitor center is adjacent to the Wupatki ruins and contains interesting exhibits on the Sinagua and Ancestral Puebloan people who once inhabited the region. November through March, there are reservation-only guided hikes on Saturdays.