A Dakhma (Persian: دخمه ; Avestan: lit. “tower of silence”), also called a Tower of Silence, is a circular, raised structure built by Zoroastrians for excarnation – that is, for dead bodies to be exposed to carrion birds, usually vultures.
The English language term "Tower of Silence" is a neologism attributed to Robert Murphy, a translator for the British colonial government of India in the early 19th century.
There are two towers near Yazd, built in the nineteenth century according to a design from India, where many Zoroastrians live. At the terrace at the top, the dead were exposed, and devoured by birds. In this way, neither the earth nor the sacred fire were soiled.
In Parsi Zoroastrian tradition, exposure of the dead is also considered to be an individual's final act of charity, providing the birds with what would otherwise be destroyed.
Although the towers date back to the nineteenth century and are influenced by the practices of Indian Zoroastrians, the custom to expose the dead on towers is mentioned in the late Sasanian age.
Zoroastrians believe that physical and spiritual corruption go hand in hand and therefore when one draws their last breath, the body falls under the evil influence of decomposition and becomes the center of impurity. The dead body must be destroyed to prevent the spread of impurity. As a Zoroastrian must not contaminate any of the elements, the corpse cannot be burned, or given to water or buried in the ground. Instead corpses were carried to the top of a hill or low mountain away from centers of population and sacred natural elements, and exposed to the sun in structures known as Towers of Silence. The corpse was usually moved to the tower within one day of death and during the daylight hours. The body was carried by an even number of people, even if the deceased was a child who could easily be carried by one person. The only people allowed to touch the corpse were those clothing it and the corpse-bearers. If by accident someone touched the corpse they were prohibited from coming into contact with other persons until they underwent a purification ritual that entailed ritualistic washing of the body. In the exposure procedure called ‘Khurshed nigerishn,’ which in Pahlavi means ‘beholding by the sun,’ the dead were placed on top of the tower, which has an almost flat roof divided into three concentric rings with a perimeter slightly higher than the center and is open at the top to give access to the body to birds. The bodies of men were arranged around the outer ring, women inside the second circle, and children in the innermost ring. When the sun disintegrated the body and birds stripped it of flesh, the remaining bones were placed in the Ossuary Well. Towers of Silence were built of mud brick, stone and stucco to protect the ground from contamination. Dakhme is located outside the city and built with precise calculations so that the wind would not carry pollutants back to the city. Ever growing cities and towns that placed Towers of Silence within city limits resulted in the Zoroastrians of Iran to stop using these towers in the 1970s and to begin using new burial methods such a laying the body of the deceased in plastered graves lined with rock to prevent the contamination of the earth.
The decision to change the system was accelerated by three considerations: The first problem arose with the establishment of the Dar ul-Funun medical school. Since Islam considers unnecessary dissection of corpses as a form of mutilation, thus forbidding it, there were no corpses for study available through official channels. The towers were repeatedly broken into, much to the dismay and humiliation of the Zoroastrian community. Secondly, while the towers had originally been built away from population centers, the growth of the towns led to the towers now being within city limits. Finally, many of the Zoroastrians themselves found the system outdated. Following long negotiations between the anjuman societies of Yazd, Kerman, and Tehran, the latter gained a majority and established a cemetery some 10 km from Tehran at Ghassr-e Firouzeh (Firouzeh's Palace). The graves were lined with rocks and plastered with cement to prevent direct contact with the earth. In Yazd and Kerman, in addition to cemeteries, orthodox Zoroastrians continued to maintain a tower until the 1970s when ritual exposure was prohibited by law.