Zoroaster was a Persian prophet and founder of the ancient Iranian religion baring his namesake. There are huge amounts of things to say about him and the lineage of his teachings, which have found traces of their influence winding all the way down into modern disparate practices. But that's another story. In general, Zoroastrianism has it that good agencies and bad agencies or rigorously defined and incompatible. For example, the Zoroastrians believe that anything dead, from bodies to nail clippings, are Nasu: contaminated, unclean and entry points for evil. They cannot be put into the ground as they will infect the earth and they cannot be burned as fire is a pure element. The practice then became to build large circular structures with their openings perpetually exposed to the sun and birds. These are known as a Dakhma (or for us english speakers a Tower of Silence.) The design consists classically of open air concentric circles; corpses of men would be tossed into the outer most rings, the women in the middle areas, and the children into the center. After however long it took to get all the way down to bone, groups of the specifically ordained could enter the Dakhma to collect the leavings and dissolve them in lime baths before eventually sending them down filters and water routes out to the sea.