The Indians also practiced slash-and-burn agriculture, hardly environmentally friendly.
Someone else posted how advanced the Azteces were compared to the contemporary Dark Age civilization in Europe. Well,first the Aztecs were not contemparies with Dark Age Europe. Second, Europe was still capable of architectural masterpieces throughout the First Millennium; the Hagia Sophia in Constantinople dates from the Sixth Century, for instance.
Look up the torture-murder of Col William Crawford in Ohio, by Shawnees (I think). Alan Eckert details the gruesome procedure in a couple of his books (although the accuracy of his history is not as good as it should be). Crawford's ordeal, though, is pretty well documented, and Eckert is a pretty accessible source.