Before the Sassanid Empire, in today's Iran, was conquered and Islamized by the Arabs in 636 AD, the majority of Persians belonged to the religion of Zoroastrianism, whose founder was Zoroaster.
Already in the 7th to 4th century BC Zoroastrianism spread throughout the entire Persian cultural area. Even today there are still about 120,000 Zoroastrians in today's Iran, Pakistan and India.
The preferred form of burial for Zoroastrians is the so-called sky burial. This means that the deceased are placed on a "tower of silence" (Dachma) where the flesh and soft parts are eaten by birds such as vultures and ravens. The remaining bones are then thrown into a pit in the middle of the tower.
Apart from a mortician, no one had access to the Dachma. The latter was forbidden to enter the city to prevent him from spreading diseases.
The origin of this form of burial is probably due to the lack of firewood and a hard (or frozen) ground, which is why it is also common in Tibet and Mongolia.
Later on, this form of burial was usually also religiously justified. For the Zoroastrians not only air and water, but also earth and fire are sacred and may not be contaminated by the unclean cadaver, so that earth and fire burial are ruled out.
In the 1970s, however, sky burial was prohibited in Iran, as it occasionally happened that birds dropped body parts over inhabited areas.
In Yazd in Iran there is still a large community of Zoroastrians.
Just outside the town on two mountain peaks, you can visit two "towers of silence".
Especially at sunset you can still feel that this place has its own morbid history.
PS: If you think that it is "barbaric" or "uncivilized" to let the dead be eaten by birds, you should ask yourself if it is really so much more "civilized" to let the dead be eaten by worms and maggots ;-)