In Mexico's Yucatan Peninsula the 30-metre high El Castilo step pyramid was the centre piece of Chichen Itza, a holy city of the Mayan civilization controlled by priests and maintained by the labour of the local peasantry. The principal gods in the Mayan pantheon were associated with the forces of nature and creation, and since Yucatan was an arid, sunbaked land the greatest boon to be requested of these deities were rain, fertility and a plentiful harvest of corn.

At rainmaking ceremonies, priests burnt a kind of resin which gave off a thick black smoke in simulation of rain clouds. To calculate the appropriate times for planting and ritual, the Mayans relied on the outstanding knowledge of their astronomers who had developed a remarkably sophisticated system of time keeping. El Castillo itself was designed partly as an architectural diagram of the calendar; its four flights of steps, 364 in all to which was added one more, up to the temple's sanctum, for a total number equal to that of a solar year.

Around the year 1,000 Yucatan was invaded by the Itza tribe, who brought with them the cult of a feathered serpent god and the practice of human sacrifice, learnt from the Toltecs of Northern Mexico. At rainmaking ceremonies and other major sacrificial rites worshippers, assembled at the base of the temple, while the nobles drew barbed thongs through their tongues and ears, spilling their blood on to pieces of bark for presentation to the gods. Above them in the sanctum children tied to the altar raised their voices in imitation of frogs, whose croaking heralded the coming of rain.

Gorgeously attired priests divided into different orders officiated at the ceremonies. One order held the arms and legs of the victim - often prisoners of war - while another split open their chests with flints to pluck out their hearts. The lifeless bodies were then hurled down the pyramid steps and submerged, together with offerings of gold, jade and copper, in a nearby well