Yushu remains nomadic culture's permanent home. Erik Nilsson explores the iconic settlement in the extreme elevations of yak country.

Yushu's legacy as a bastion of Tibetan culture is literally written in stone. That is, the high-altitude prefecture in Qinghai province hosts the world's largest collection of mani (prayer) stones-an estimated 2.5 billion-some as small as pebbles, some as big as boulders.

Pilgrims purchase stones carved with scriptures or sacred images and place them on the Seng-ze Gyanak Mani Wall.

Craftspeople carve the inscriptions on-site and take custom orders, such as prayers for deceased relatives. The sounds of their chisels striking the rocks echo off the mountains, providing percussion that accompanies the droning chants of the devout and tinkling of bells slung around the necks of yaks that clip-clop through the site.

Pilgrims spin prayer wheels beneath prayer flags as they circle the prayer stones, which cover an area roughly the size of a city block.

They also burn incense, as the smoke is believed to carry their prayers to heaven, and juniper branches, whose fragrance is believed to cleanse the soul.

The first stones were laid in 1715, and people have since continued to enlarge the walls day by day, stone by stone, as if building a colossal anthill.

Yushu's magnitude 7.1 quake in 2010 scattered the mantras like the shards of a dropped porcelain vase. But they were quickly put back in place by the faithful.

The wall is a superlative attraction but far from the only place that makes Yushu an ideal destination to engage Tibetan culture.