As we go west, the mosque minarets, where no muezzin is allowed to call, taper above the roofs in fantastical belvederes and colonettes, or stand like filigreed toys along the heights which shadow us to Labrang.

Then suddenly, beyond Linxia, the loess hills have gone, and our valley steepens into stone. A young monk climbs on board, and smiling Tibetan herdsmen in dented felt hats. The shoulders of unseen mountains drop towards us out of the clouds. Once, some police stop the bus and we are all emptied on to the verge while a man sprays disinfectant over the floor. The Sars virus has erupted in Xian to our east. The leftover Chinese hook on white masks. The Tibetans go on smiling.

Soon we are travelling up a steep, misty corridor. The river flows faster, purer, the colour of pale jade. The mountains close in. We have crossed a border unmarked by any map, already infringing on the plateaux of Tibet. The Buddhist stupas sit like nipples on the hills, while prayer-flags fly from the house courtyards and rustle over cairns in the pastures. Here and there, set far up a hillside, the tiered roofs of a monastery cascade to white walls. Then the road disintegrates to a gravel track. In the dusk the slopes are stamped with the shapes of sleeping yaks, and snow is falling in a soft, thin silence.

I disembark into the night and cold of Labrang. I am still more than 300 miles from the Tibetan frontier. Lights fade down the street where Hui and Chinese shops have settled beside the monastery town beyond. My feet crunch over the snow, seeming light and lonely, and from somewhere in the darkness ahead — like an old god clearing his throat — sounds the braying of a horn. Then a familiar elation wells up: the childlike anticipation of entering the unknown, some perfect otherness. Your body lightens and tingles. The night fills up with half-imagined buildings, voices you do not understand. The experience is inseparable from solitude and a vestigial fear, because you don’t know where the road will end, who will be there.

As it is, the street empties and I cross a rubbish-filled dyke into the unlit Buddhist quarter, and turn by chance into the monastery guesthouse. It is a courtyard of naked rooms, frosty with trees. Besides a caretaker, I glimpse only the herdsman pilgrims lumbering from door to door, huge against the snow in their swathing coats.

My room has a wooden bed and a pail for collecting water from the communal tap. A coal-burning stove sends a wonky chimney through a hole in the ceiling. A lightbulb hangs from a wire. The room costs fifty pence a night. I stretch out under a damp quilt, and listen to the faint, brittle snap of twigs outside as the snow settles.

THE MONASTERY grew up 300 years ago under the tutelage of local Mongol princes. A stronghold of the Yellow Hat sect, to which the Dalai Lama belongs, it became one of the six great lamaseries of the Tibetan world. Its curriculum was liberal in its way, tinged by the shamanism of local nomads, but rooted in meditation and theology, and in Buddhist medicine and mathematics. By 1959, when the Tibetans rose against China and the Dalai Lama fled, it sheltered 4,000 monks.

Then came mass arrests and expulsions. The library of 10,000 manuscripts burnt to the ground. In the Cultural Revolution half its temples were levelled. Only in 1980 did the monastery cautiously reopen; the monks started to filter back, and novices came from Tibet, Qinghai, Inner Mongolia. Now there were over 2,000, and in the dawn snow the pilgrims’ bootprints already trailed out of the hostel toward their old sanctuaries. I cleaned my teeth in the snow. The communal tap was frozen. The lavatory was a line of holes above a pit, where I squatted in a row of jovial herdsmen, whose windburnt faces cracked into grins. One wore a silver medallion of the young Dalai Lama, which he concealed again in the folds of his coat.

Outside, feathers of snow were still falling. In the whitened sky the mountains left only the tracery of their stone, like stencils hung in nothing. I followed a curved track between the walls of the monks’ fraternities. There was no sound but the dripping of snowmelt from the eaves, and the lisp of water in the open drains. Suddenly, ahead of me a cluster of pilgrims fell to their knees. Up the long avenue between the monks’ cells, misted in falling snow, I saw far away — like the backdrop to some sacred drama — the crests of gilded temples glinting against the mountains. They rose in facades of oxblood red, then mounted to green and mustard-yellow tiles, while beyond them again the farthest shrines banked upward in a surge of golden roofs. Beneath this unreal city, the magenta and purple robes of the monks were drifting back and forth.

But as I approached them, the buildings separated into rough-built halls and fort-like gates. Their height was an illusion. The distinctive facades — a deep oxide red — were built of compacted twig bundles, long dry. The rooftops teemed with golden griffins, the deer of Benares, the Wheel of the Law. Dragon gargoyles leered from their eaves. All was earthy, vivid, strange.

Under the arcades of the philosophy hall, 300 monks waited in casual conclave, wrapped in magenta and crested in yellow cockscomb hats. The young were innocently boisterous, thumping and tussling together. They greeted me in rough Chinese, and foraged for news of the Dalai Lama. Outside, they were snowballing one another. But a senior monk beckoned them by groups into the shrine, and from there the guttural prayers stirred like the drone of bees, or a mantra muttered in sleep.

I slipped into the sanctuary beside them, enclosed among avenues of pillars. Twenty years ago the hall had been swept by fire — an electrical fault, the monks said — and now it was lit only by a glimmer of butter lamps and the wintry light dying through its porticoes. The monks had dwindled in its gloom, squatting round their teachers in broken semicircles. I walked here alone. The pillars were draped in cloth, as if they were alive, and faded to darkness down glades of synthetic colour.

A thousand tiny, identical Buddhas covered the side walls, and across the deepest recess, perched on clouds and lotus thrones, a double rank of reincarnate saints filled the dark with their dreamy power. Their fingers held up flowers and bells, or cradled thunderbolts. Yak-butter lamps and hundreds of candles stranded each in a zone of orange fire. Here sat the multiform Bodhisattvas, blessed beings who had delayed their entry to nirvana in order to save others. Monastic founders perched gold-faced in pointed wizard’s hats, and demon guardians — the countervailing faces of death — danced with necklaces of skulls or severed heads. Everywhere divinity branched and proliferated — many-headed, multi-armed — loving, death-dealing, indifferent.

On one altar I noticed three photographs. They were of the past three incarnations of the Panchen Lama, second in holiness only to the Dalai Lama. The last was a rosy-cheeked boy in a peaked hat.

Where was he now, I asked.

“I believe he is in the Chinese capital,” a young monk said, not meeting my eyes. The chosen Panchen Lama had been taken away by the Chinese and never seen again. They had cynically substituted one of their own.

And where was the Living Buddha of Labrang, I wondered. He was in Lanzhou — the monk said unhappily — serving in the Ministry of Religion. So he too had been sterilised. The monk beckoned me away. “Here,” he said a little desperately, steering me to other statues, “are the two most important Buddhist philosophers.”

“Who are they?”

“I’m sorry...” he looked crestfallen, “I do not know.”

How long had he been here?

“I came 12 years ago, from a village near here. I was 14.”

“Why did you come?”

“Because my mother and father wanted it. At the time I knew nothing. Then the world became strange for me. Everything very strange. I understood nothing at all.” He spoke as if he still did not understand. He looked far younger than his years: a shy youth with a dust of moustache. “We pray a long time, three times a day. We may study all day, or just an hour or two. It never ends.”

I went out into the labyrinth of the monastery, following the groan of horns. I attempted to gain entrance to closed courtyards, forbidden halls. The palace of the Living Buddha, the monks said, had been locked up for years. The relics of his forerunners lay under gilded stupas. In another temple these ancestral Buddhas had been intricately sculpted in yak butter for the Buddhist New Year: high-coloured saints who would melt with the summer. Once only I saw a photograph of the Dalai Lama — put up before he fled, a monk said, and so it had remained: a cloudless face, from the time of peace.

Along the galleries of prayer-wheels, and threading between all the shrines, the pilgrims marched in dogged, hungry devotion: Tibetans and Mongolians from the grasslands, their hair matted and wild, mysteriously happy. Their ankle-length robes, trimmed with lynx or fox, transformed them to giants in brilliant cuffs and sashes. Their cheekbones surged under coppery skin, the women’s sometimes wind-flayed scarlet, as if by rouge. Often their coats eased off their shoulders, and their enormous sleeves trailed unused along the ground. Then the women’s robes would part casually on an arsenal of coral and turquoise jewellery; and belts dangled silver pendants. Their hair fell to their waists in two glistening cables, linked high up by silver clasps.

What were they seeing? What did they expect? They tramped in robust euphoria. Divinity to them was everywhere. You might touch it with your hand. Turn a prayer-wheel, light a butter lamp, and something was set in motion. Wizened elders and tiny matriarchs tapped their foreheads at temple doors and caressed the votive scarves which hung there. The perpetual breath of their prayer, Om mani padme hum, sighed like a low heartbeat. Some prostrated themselves full length in a clatter of bangles, drew their bodies forward to their outstretched hands, rose, fell again, and sometimes circled the temples or the whole monastery like this, their palms blistered, their hair clogged with mud, in a state of unearthly grace.
 
Extracted from Shadow of the Silk Road by Colin Thubron, published by Chatto & Windus at £20. To buy it for the reduced price of £18, with free p&p in the UK, call The Sunday Times Books First on 0870 165 8585

Travel details: this off-the-beaten-track region of China is best tackled using the expertise of a specialist tour operator, such as Silk Road
and Beyond (020 7371 3131, www.silkroadandbeyond.co.uk), which offers a 12-day trip, visiting Beijing, Lanzhou, the Labrang Monastery and Jiayuguan, from £1,750pp. The price includes flights with Air China from London to Beijing, domestic flights, B&B accommodation and guiding. Or try CTS Horizons (020 7836 9911, www.ctshorizons.com) or Steppes East (01285 651010, www.steppestravel.co.uk).