If you're making a visit to Chaco Culture National Historical Park this summer and your plans include camping, be sure to do some homework in advance. The campground in the park is currently closed for emergency repairs—and don't count on your trusty GPS unit to find a backup site!

Scientists continue to puzzle over the extensive, carefully engineered road system that Ancestral Puebloans built ten centuries ago in the San Juan Basin of the Colorado Plateau. What functions did this prehistoric road system serve, and what accounts for its quirky design features?