The world as seen by the Maya
The Mayans viewed the Earth as flat and four cornered, with one corner in each cardinal direction. Each direction had a color: red for east, white for north, black for west, yellow for south and green for the center. The sky was supported by four trees, one in each corner and one at the center. The trees were all different colors. The Earth was on the back of a giant crocodile resting in a pool of water lilies. The crocodile's counterpart in the sky was a double-headed serpent. This is probably because the Mayan word for sky was close to the Mayan word for snake. Heaven had 13 layers. Each layer was associated with a different god. The underworld had nine layers, each associated with a Lord of the Night. The underworld was a cold and unhappy place. Most Mayans went to the underworld after their death.
The detailed astronomical observations of the Mayans area recorded in the Codices, especially the Dresden Codex. The Mayans observed many celestial objects with great precision (including Venus in the Dresden Codex). They had a complex calendar that cycled every 5200 years. The Mayans used base 20 for all their math. They also used zero, the only independently developed use of zero in the Americas.
The Mayans had the Popol Vuh, which means Book of Counsel). This was a kind of bible. It had myths and legends probably based on real events in the distant past. In it, the Hero Twins defeat the lords of the underworld and create the path of resurrection for humanity. The Mayans also had The Books of Chilam Balam, which means jaguar priest. These books contain information about Mayan medicine, astronomy, and astrology. It also contains historical information about the Yucatec region previous to European contact