The way that Mesoamerica built their civilization in isolation from the old world is intensely fascinating (example: making farm land in the middle of lakes). The uniqueness in the way they extracted resources to what was considered valuable gives insight into the way humanity develops. The Mexica Empire/Valley of Mexico Triple Alliance/The Tenochca Empire/Aztec Empire is particularly interesting due it's success being derived from an abundance of practices already in place rather than innovation (they revved up everything to an 11). Their approach to warfare emphasizing one on one combat was dramatic. Finally their methods of human sacrifice are some of the most metal things I've ever heard to the point where I find violence in fiction to be banal by comparison.