to lowland and coastal Mesoamericans creating a further disincentive to settle down in permanent communities. Political organization Ceremonial centers were the nuclei of Mesoamerican settlements. The temples provided spatial orientation, which was imparted to the surrounding town. The cities with their commercial and religious centers were always political entities, somewhat similar to the European city-state, and each person could identify with the city where they lived. Ceremonial centers were always built to be visible. Pyramids were meant to stand out from the rest of the city, to represent the gods and their powers. Another characteristic feature of the ceremonial centers is historic layers. All the ceremonial edifices were built in various phases, one on top of the other, to the point that what we now see is usually the last stage of construction. Ultimately, the ceremonial centers were the architectural translation of the identity of each city, as represented by the veneration of their gods and masters. Stelae were common public monuments throughout Mesoamerica, and served to commemorate notable successes, events and dates associated with the rulers and nobility of the various sites. Economy Given that Mesoamerica was broken into numerous and diverse ecological niches, none of the societies that inhabited the area were self-sufficient, although very long-distance trade was common only for very rare goods, or luxury materials. For this reason, from the last centuries of the Archaic period (8000 BC– 1000 BC) onward, regions compensated for the environmental inadequacies by specializing in the extraction of certain abundant natural resources and then trading them for necessary unavailable resources through established commercial trade networks. The following is a list of some of the specialized resources traded from the various Mesoamerican sub-regions and environmental contexts: Pacific lowlands: cotton and cochineal Maya lowlands and the Gulf Coast: cacao, vanilla, jaguar skins, birds and bird feathers (especially quetzal and macaw) Central Mexico: Obsidian (Pachuca) Guatemalan highlands: Obsidian (San Martin Jilotepeque, El Chayal, and Ixtepeque), pyrite, and jade from the Motagua River valley Coastal areas: salt, dry fish, shell, and dyes Architecture Mesoamerican architecture is the collective name given to urban, ceremonial and public structures built by pre-Columbian civilizations in Mesoamerica. Although very different in styles, all kinds of mesoamerican architecture show some kind of interrelation, due to very significant cultural exchanges occurred during thousands of years. Among the most well-known structures in Mesoamerica, the flat-top pyramids are a landmark feature of the most