Did you know there were observatories in Mayan times? This is El Caracol, or 'The Snail', which has windows and doors aligned to astronomical events. http://www.trafalgar.com/treasures-of-the-yucatan-2014
Tenochtitlan, a.k.a The Impossible City. Found in 1324 by the Aztecs on a small land. Aztecs added man-made land to expand the surface area with mud, grass, etc. Aztecs were wheel-less and may have had canals just like Venice, Italy. Medicine was sophisticated.