The Maya are probably the best-known of the classical civilizations of Mesoamerica. Originating in the Yucatán around 2600 B.C., they rose to prominence around A.D. 250 in present-day southern Mexico, Guatemala, northern Belize and western Honduras. Building on the inherited inventions and ideas of earlier civilizations such as the Olmec, the Maya developed astronomy, calendrical systems and hieroglyphic writing. The Maya were noted as well for elaborate and highly decorated ceremonial architecture, including temple-pyramids, palaces and observatories, all built without metal tools. They were also skilled farmers, clearing large sections of tropical rain forest and, where groundwater was scarce, building sizeable underground reservoirs for the storage of rainwater. The Maya were equally skilled as weavers and potters, and cleared routes through jungles and swamps to foster extensive trade networks with distant peoples.