The landscape northeast of Flagstaff is a desolate, sparsely populated region carpeted with volcanic ash deposited in the 11th century. The area also contains hundreds of archaeological sites, the most impressive being the pueblo ruins left by the Sinagua (“wupatki”  means “without water” in Spanish), who inhabited this area from around 1100 until around 1250. Contemporary Hopis and Zunis claim them as their ancestors, and it is easy to see the similarity between the stone-walled pueblos here and traditional homes on the nearby Hopi Reservation. Today the ruins of several ancient villages are preserved in this national monument, the largest being 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 courts built by the Aztec and Maya peoples farther south, suggests a similar game was 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: Nalakihu, Citadel, and Lomaki are the closest to U.S. 89; Wukoki, built atop a huge sandstone boulder near Wupatki, is particularly picturesque. The visitor center adjacent to the Wupatki ruins has some interesting exhibits on the Sinagua and Ancestral Puebloan people. November through March, there are reservation-only guided hikes on Saturdays. All hikes begin at noon and last from 2 to 3 hours.