The Ancient Mayan civilization had a complex society that was organized into classes. At the top were nobles and priests, followed by warriors, craftsmen and traders, with farmers, workers and slaves at the bottom. The Mayans were skilled farmers, weavers, and potters, and they developed advanced calendars, astronomy, mathematics and hieroglyphic writing. They built large cities with temples, palaces and pyramids and believed in many nature gods, practicing human sacrifice in religious rituals.