As with all myths of the Maya, there are different versions of the cosmology in different centers. Generally it was believed that the earth (Cab) was a flat surface with four corners representing the four directions and the four cardinal colors—red, white, black, yellow. The flat surface for some was actually the back of a giant crocodile. As for the sky, it too had four corners and was held up by four powerful gods, known as the Bacab, and/or by a world tree, the Yaxché (Ceiba Tree), which stood in the center of the whole cosmos. The sky equivalent of the earth crocodile in some traditions was the two-headed serpent. There were many layers of heaven (Caan), each controlled by a god. At the highest level was the Maize god, Hunab’Ku, the father of the sacred twins. The Underworld (Xibalba, or Metanal) also had many layers and was visited each night by the Sun.