Wupatki National Monument houses the remains of one of the largest, ancient Native American settlements in the US. The Wupatki Pueblo Trail, a half-mile, self-guided tour of the largest pueblo in the Flagstaff area, starts at the visitor center.
A short and very easy hike to the Wupatki Pueblo is worth your efforts. The kids were interested in seeing how people had lived so many years ago (my 6-year-old was quite amazed that people lived here BEFORE I was born!! :))
It was quite windy while we visited, so we didn't stay very long, but the architecutre and size of this structure were truly amazing.
The visitor center has nice clean restrooms, plenty of hands on gadgets and information about the original inhabitants and even some information on the sad take over of this property from the Indians by the US government.