This is a hard question to answer because there is simply so much to say. The incans, Aztecs, olmecs and Mayans were all vital civilizations in the americas to be “in the knowing” about. However the Aztecs were the last before the European arrival of memory serves correctly. Their capital city was tenochtitlán which is around the current place Mexico City now resides. Two years after the Spanish came to the Americas the Aztec empire had declined. They were really passionate about the sun god as well and sacrificed humans to keep the sun god (and the gods) appeased.