"18-Rabbit's master masons shaped the central door of his temple to represent the mouth and gullet of the great Witz Monster. This was meant to indicate that the interior of the temple symbolized a living cave that opened into the heart of the mountain. To the Classic Maya, all natural openings into the earth, whether caves or cenotes (sunken waterholes), were portals to the Otherworld. Their architecture echoes this belief. Deep behind this cave door stood the sanctum where 18-Rabbit and his successor conjured up their ancestors and the gods."
Freidel, Schele, Parker, Maya Cosmos: Three Thousand Years on the Shaman's Path, p. 149-50