Thriving from 100-750 A.D., Teotihuacan was one of the largest cities in the ancient world, with a population estimated at upwards of 150,000-250,000, over three times the size of contemporary Mayan capitals. Furthermore, Teotihuacan was a supremely well-planned and efficient city that was able to field massive armies and extend its power far beyond its home base to create a unified empire unlike anything in the region before it. In fact, the city's residents seemed so sure of its power that there were apparently no walls or military fortifications around Teotihuacan. Thanks to that power, Teotihuacan not only served as a vital center for trade in Ancient Mesoamerica but also spread its architecture, art, religion, and culture, all of which subsequently influenced the famous Mesoamerican civilizations that followed, including the Aztec and Maya.
Chichen Itza was inhabited for hundreds of years and was a very influential center in the later years of Maya civilization. At its height, Chichen Itza may have had over 30,000 inhabitants, and with a spectacular pyramid, enormous ball court, observatory and several temples, the builders of this city exceeded even those at Uxmal in developing the use of columns and exterior relief decoration. Although Chichen Itza was around for hundreds of years, it had a relatively short period of dominance in the region, lasting from about 800-950 A.D.
Today, Machu Picchu is one of South America's best tourist spots, and the ruins have even been voted one of the Seven New Wonders of the World. But even though Machu Picchu is now the best known of all Incan ruins, its function in Incan civilization is still not clear. Some have speculated that it was an outpost or a frontier citadel, while others believe it to be a sanctuary or a work center for women. Still others suggest that it was a ceremonial center or perhaps even the last refuge of the Incas after the Spanish conquest.
