Location The skull wall is near the Duoduoka Charnel Ground in the western part of Biru County, 300 kilometers southeast Naqu in Tibet Autonomous Region. The name "Biru" originally meant the "horn of female Tibetan yak", according to a local saga, a "tribe of female yak" once settled down here.

About celestial burial Legend has it that Zhigungba Renqenbai set up the Zhigungti Monastery in Maizhokunggar County in 1179, and worked hard to press ahead with perfecting the celestial burial (or sky burial) system to mark the legendary fact that Sakyamuni, founder of Buddhism, cut off his flesh to feed a tiger. However, an analysis of what have been found from some ancient tombs in Tibet shows that the system began in the 7th century.

When a celestial burial ritual is held, aromatic plants are burnt for smoke to guide the soul to reach the Ground. The human body serves as a sacrificial object to the Goddess and other deities, who are requested to take the soul of the dead up to Heaven. As a matter of fact, smoke resulting from burning aromatic plants lures the hawks, "holy birds'' in the eyes of the Tibetans.

The body is laid on a piece of stone slab measuring 60 cm high, which lies by a pond built with pebbles. The body, in a sitting stance, is sliced. Its bones fall prey to hawks first. The Master in charge of the ritual does so because hawks tend to shun bones. Introduction The skull wall is a result of Tibet's unique celestial burial tradition. The Duoduoka Charnel Ground occupies an area of about 4,000 square meters.

Earthen walls roughly as tall as a man stand on the ground's four sides. On the south and west walls, there are some wooden shelves, between four to five stories each, each shelf displaying some orderly-placed human skulls. There are two gates respectively on the west and south of the Duoduoka Charnel Ground's courtyard. The west gate is for living human beings, while the one on the south is where the bodies are carried in.

The bungalow on the north is exclusively for the monks who carry out the religious celestial burial ceremonies, and inside the rooms are some religious scriptures and figures. Beneath the courtyard of the charnel ground is a cellar, whose floor and walls are built of stones, and which stores Buddha figures, the Tripitaka (the three major parts of Buddha's teachings), and religious tools and sacrifices.

In the center of the Duoduoka Charnel Ground lies a celestial burial pool of about foursquare meters made of small cobbles. On the pool's north stands a rectangular stone about 60 cm above the ground. The stone is used to hold the bodies in celestial burials. A pole more than ten meters tall with some prayer flags hung on top stands outside the charnel ground's south gate. The winter here can be extremely cold, sometimes falling as low as 37-Celsius degrees below zero.

However, no matter how frozen the body is, following a night in the celestial burial pool, it will surely unfreeze the next day, thus ensuring a smooth celestial burial. Nobody yet can explain this phenomenon. This mystery has made the Duoduoka Charnel Ground even more famous, even attracting some people from neighboring counties to choose it for their own death.

Relative Legends According to Duoduoka's celestial burial master, there were originally three monasteries where skulls were kept after celestial burials: the Duoduoka Monastery, the Ridazeng Monastery opposite the former and the Quedai Monastery nearby. Biru has gained its fame from containing all three monasteries. Unfortunately, most of the skulls have been damaged both by natural and manmade disasters.

By the early 1980s, most of skulls in the Ridazeng and Quedai monasteries have disappeared, despite a very supportive governmental policy in preserving religious relics. But why skulls are kept in the celestial burial of these three monasteries remains a mystery. There are currently many versions of this unique custom's origin, but two possible answers are prevailing and more accepted.

One version says that the custom was formed some 80 years ago, when an eight-year-old boy from a Tibetan tribe witnessed the killings of three people. The little boy was so scared that he ran directly to the living Buddha in Biru County, who later appointed him as a celestial burial master. He began to pile up all the skulls of the dead in the corners of the charnel ground.

At his death, 42 years later he left behind a wall of skulls. It is said that he built the skull wall to prevent the killer he saw when he was eight from coming to the charnel ground. The other version retains that the custom is a rule established by a living Buddha, whose motives remain unknown.

According to Awangdanzeng, a celestial burial master, the main purpose of keeping the skulls and piling them up against a wall is to remind the living to do more good deeds and restrain from secular desires, because everybody, regardless of their living status, is the same after death.