seems to signal a decisive war ("star war"). Some of the Books of Chilam Balam testify to the great interest the colonial Maya had for the astrology of their conquerors. Cosmology Earth, sky, underworld Horizontally, the earth is conceived in various ways: as a square with its four directional or, perhaps, solstice points, or as a circle without such fixed points. The square earth is sometimes imagined as a maize field, the circular earth as a turtle floating on the waters. Each direction has its own tree, bird, deity, color, and aspect, in the highlands also its own mountain. Vertically, the sky is divided into thirteen layers, and Classic period deities are sometimes linked to one of the thirteen skies. By analogy with the 'Nine-God' mentioned together with the 'Thirteen-God' in the Chilam Balam book of Chumayel, the underworld is often assumed to have consisted of nine layers. However, the Popol Vuh does not know such a ninefold division, and Classic period references to layers of the underworld have not been identified. In the world's centre is a tree of life (the yaxche 'ceiba') that serves as a means of communication between the various spheres. In Palenque, the tree of life is a maize tree, just as the central world tree in the Borgia Codex; a curving bicephalic serpent hovers around it, which some believe to embody the ecliptic. The king was probably identified with the tree of the centre and is usually shown to carry the bicephalic serpent as a ceremonial bar. Besides worshipping a central maize tree, the king commonly sits or stands on a mountain containing the maize, perhaps as a guardian of the kingdom's maize supplies. In the Classic period, earth and sky are visualized as horizontally extended serpents and dragons (often bicephalic, more rarely feathered) which serve as vehicles for deities and ancestors, and make these appear from their maws. Other serpents, shown as vertically rising, seem to connect the various spheres, perhaps to transport the subterranean or terrestrial waters to the sky. Dragons combine features of serpent, crocodile, and deer, and may show 'star' signs; they have been variously identified as the nocturnal sky and as the Milky Way. World endings and beginnings Within the framework of the post-Classic cycle of thirteen katuns (the so-called 'Short Count'), some of the Yucatec Books of Chilam Balam present a deluge myth describing the collapse of the