This documentary explains the evidence of the Pueblo Period in what is now the U.S., spanning from 1000 - 1500 AD, including the Chaco Canyon settlement in New Mexico, the Mesa Verde cliff-dwelling civilization in southern Colorado, the Grand Gulch settlement in Utah, as well as a network of roads in that region.  Also explained is how it is shown that cannibalism happened at the end of that civilization, likely being due to war-like peoples coming from the south who were potentially precursors to the Mayans, and it is shown that the people in the area likely migrated south to the Arizona region due to the onset of a drought.