Chaac (Chahk) is the rain and storm god of the Maya, one of the most important and most frequently depicted deities of the whole tradition, unsurprisingly, in a farming society dependent on seasonal rain for its maize. He is recognizable by a long, curling, pendulous nose or snout, reptilian features, and a lightning-axe or serpent that he wields to strike the clouds and loose the rain; images of him crowd Maya ceramics, codices and the facades of buildings, where masks identified with the rain-god (long called Chac masks) are repeated across whole walls, as at the Puuc sites of Yucatan. He is often reckoned as four, one for each of the world-directions with its associated colour.
The clearest single monument to Chaac's visual importance is the Codz Poop, the Palace of the Masks, at the Puuc site of Kabah in Yucatan, whose entire main facade is covered with several hundred individually carved stone Chaac masks stacked in repeating vertical rows, an unmatched concentration of the rain-god's image on a single building anywhere in the Maya world. Related but less extreme repetitions of the long-nosed mask appear across other Puuc-style buildings, including the Nunnery Quadrangle at Uxmal, showing how central Chaac's invocation was to the architectural decoration of this particular Late Classic regional style, more than for almost any other Maya deity.