The engineering abilities of the ancient Pueblo people are truly astounding and evident at Chaco Canyon National Historical Park. Thousands lived in the canyon from 850 AD to 1250 AD. Designated a UNESCO World Heritage site in 1987, it is a place that if you visit New Mexico, you should take a day and explore. (the last part of the drive to the site is on unpaved road about 16 miles - but totally worth it!).