The Zoroastrians believe that death is evil triumphing over good and, once the body is dead, demons have the ability to contaminate the corpse. As the bodies could pollute everything due to their uncleanliness, a system of funerary rites was developed to ensure the body was disposed of as safely as possible. Hence the Dakhmas, or Towers of Silence, were born over 3000 years ago.
Towers of Silence were cylindrical structures built of concentric stone slabs circling a central pit, and were typically built at the tops of hills. The corpses of the deceased were placed onto one of four concentric platforms, with men at the outermost ring, followed by women, and with children in the centre.
Much like with the Tibetan Sky Burials, these bodies are left at the top of the Towers of Silence to be consumed by carrion birds. The Zoroastrians believed the four elements are sacred, thus an unclean body could not be disposed of by water or by burial, and certainly not cremated by fire, believed to be the purest of the elements.
Even though the bodies would be picked clean in a matter of hours by the carrion birds, the bones of the dead were left at the tops of the towers to bleach in the sun for a year or longer, before the guardian of the tower would come and push the bones down into the ossuary pit below. There, the bones would be ground up and purified with a series of coal and sand filters, before the fine powder that remained would be washed into the sea.
In Iran, the use of dakhmas continued into the 1970s, until the practice was banned, forcing devout Zoroastrians to embrace new funerary practices. The dakhmas of Iran are considered to be the best examples of their kind worldwide. You can also find the Towers of Silence, outside Mumbai in India, which, dating back to the 4th and 5th centuries, can also be visited.