High in the Himalayas, a barbed wire fence snakes its way across a desolate landscape. On most days, a thick, white, freezing cloud descends across the peaks, and it is hard to see anything. But now and then a figure looms out of the mist, dressed in combat fatigues. It is like a scene from some old war film. This is where the Chinese and Indian armies have faced off against each other across a border that has been closed for 44 years.
But now there is frenetic activity on both sides of the border. Bulldozers are clearing land. Prefabricated warehouses have been put up. At 14,400ft above sea level, the world's highest custom house is back in business: the border is about to reopen. This is the return of the Silk Road.
The narrow road that threads its way through the hills, up to the Nathu La is barely motorable, better suited to mules than trucks. But, though it may not look it today, for 58 years this road was the main artery of trade between India and China. And now Delhi and Beijing are hoping that here the Silk Road, which once accounted for a staggering proportion of the world's productivity, can be reborn.
Talks are underway between India and China in Lhasa, the Tibetan capital, for the reopening the border crossing at the Nathu La pass. If all goes according to plan, it could be open as soon as 30 June. And the Sikkim state government on the Indian side is predicting that by 2010, the total trade across Nathu La could be worth as much as $1bn (£540m).
Even if most observers think that figure is a little ambitious, there is no mistaking the significance of what is going on up at Nathu La. At this lonely mountain border post, the two fastest growing economies in the world meet. And after decades of hostility, suddenly they are hungry to invest in each others' markets.
In the 1750s, China and India between them produced a remarkable 57 per cent of the world's manufacturing output. For centuries, the Silk Road was one of the most flourishing trade arteries in the world connecting China to India, the Middle East and Europe. But in 1962, after a border war between India and China, the Silk Road was closed. The border was sealed off, and trade between the two Asian giants slowed to a trickle.
Not any more. Glimpsing the huge economic potential in co-operation, China and India have shrugged their decades-old rivalry aside. Even as the US President George Bush is courting India as a strategic ally against China, Delhi is cosying up to Beijing economically. They have marked this year as Sino-Indian friendship year, a tribute to a booming trade relationship worth £10bn last year - and that was without a direct land crossing between the two countries. It represented a rise of nearly 38 per cent from the previous year, and is certainly expected to rise this year, according to data from China's Ministry of Commerce.
In India today, the talk is of "Chindia" an economic region with vast domestic markets, where China's manufacturing complements India's IT sector.
The border between China and India lies along some of the most impenetrable mountain terrain in the world, and although there are other border crossings, they are seriously remote, and more the stuff of adventure than trade.
Which is where Nathu La comes in. Until the beginning of the 20th century, the Silk Road ran from China, across Nepal to India. But in 1904, the route across Nathu La was opened up - not for trade but for a westward expansion of the Great Game. Lord Curzon, the British Viceroy of India, became increasingly concerned that Russia could exploit Chinese weakness at the time to invade Tibet and threaten colonial India's borders. A decades-old report by a Deputy Commission in Darjeeling had spoken of the route into Tibet via the remote Himalayan land of Sikkim.
And so Lord Curzon sent for Colonel Francis Younghusband, an explorer, adventurer and mystic who could have walked out of the pages of a Victorian novel. Younghusband was dispatched to negotiate with the Tibetans - with a heavily-armed expeditionary force to back him up.
The journey across the mountains was famously so cold that ink froze. Younghusband failed in his mission, but managed to machine-gun down 900 Tibetans along the way. He did succeed in opening up the one practicable direct land route between Tibet and India - a route that was quickly taken over by trade. Traffic across the Nathu La Pass accounted for 80 per cent of the total border trade volume between the two countries in the early years of the 20th century.
That was until 1962, when it was closed. For decades, it became a symbol of Chinese and Indian hostility to each other. The once flourishing road fell silent. Troops glowered at each other. The area became deserted as inhabitants fled to more peaceful areas.
Once a week, postmen exchanged letters from mountain herders on either side of the border at the fence.
Today the atmosphere at Nathu La tells a different story. Tourists trek up to the border, and Indian and Chinese troops pose near each other for photographs. A giant sign on the Indian side provides basic Chinese greetings to call across to the Chinese soldiers on the other side.
India is predicting a tourist boom for the reopened border as well as trade. It will provide a direct route between the former Himalayan kingdoms of Tibet and Sikkim - lesser known, but every bit as exotic. It will also allow tourists to travel directly from Buddhist Tibet to the great Buddhist shrines in Bihar, in India.
Already, the newly completed trade zone has been outfitted with tourist infrastructure, including the world's highest cash point, a cyber-café and long distance telephone lines.
"The reopening of border trade will help end economic isolation in this area and play a key role in boosting market economy there," Hao Peng, the vice chairman of Tibet, said.
The Indian government is equally pleased. "The resumption of border trade is a great historic event, not only for enlarging trade, but also for greater relations between the two great countries," said Christy Fernandez, additional secretary of the Indian Department of Commerce.
But the route is not without its political implications. Tibet and Sikkim may both be exotic, but both were also formerly independent kingdoms. The reopening of the border has raised fears that Tibet's current desire for more autonomy might be crushed by the loftier ambitions of two of Asia's superpowers.
In Sikkim, too, there are concerns. Sikkim was an independent princely state with treaty agreements with British colonial India, and, unlike with most other princely states, that arrangement continued after Indian independence, until 1975, after a widespread rural revolt against the landowning monasteries and a referendum in favour, when India took control of Sikkim.
But there is growing discontent among the native Sikkimese Bhutia-Lepcha community, who, like the Tibetans, are concerned at the influx of "mainlanders" into their lands. Today they account for just 21 per cent of the population of Sikkim.
"Our main concern is being outnumbered in our own homeland," a local politician, Tseten Tashi Bhutia, toldThe Indian Express. "How long can we tolerate this? How long before AK-47s are taken up."
China has long castigated India for the claim that the Himalayan kingdom of Sikkim was an independent country "annexed" by India in 1975. That message will probably change now, as will India's tough line on Tibet, no doubt, even though Tibet's spiritual leader, the Dalai Lama, has lived in exile in Dharamsala in India since 1959.
Geographically, it certainly makes sense for Tibet to have use of the pass. Tibet currently has to import and export goods via the port of Tianjin, which is in the north-east of the country.
Chinese Communist troops entered Tibet in 1950. In matters Tibetan, Beijing sees itself as a liberating force which freed the locals of the backward yoke of a theocracy, bringing prosperity and doing much to open up the famously secretive region to modern ways. Beijing points to marvels of engineering, such as the Qinghai-Tibet railway, the world's highest, which was completed in October and is due to start operation on 1 July. While some critics say it will help swamp Lhasa with the dominant Han Chinese ethnic group, the government in Beijing sees it as a major opportunity for Tibet.
Tibet, which last year had a foreign trade volume of £109m, will benefit from resumed border trade, Hao Peng said.
"If only 10 per cent of Sino-Indian trade goes through the pass it means at least more than one billion US dollars a year," he said.
Qiangba Puncog , the chairman of the Tibet Autonomous Regional Government, pointed to economic growth of more than 12 per cent last year in Tibet, above the Chinese average, as a sign of how well the region was doing.
For India, the reopening of the road is first and foremost an opening into China's lucrative market. But the geography also neatly presents a way to improve the economy in eastern India, much of which has been left behind as the economic powerhouses of Bombay to the west and Bangalore to the south forge ahead.
Calcutta is at last beginning to show signs of emerging from its poverty, but the reopened border could present it with an opportunity for regeneration as a commercial port. And outside Calcutta, eastern India remains desperately underdeveloped. While gleaming new office buildings go up in Bangalore, in rural West Bengal people still starve to death. It is in the east that the India's Maoists have seized control of huge areas of land, riding on discontent and poverty.
But, as ever in India, the entire project may yet be held up by slow infrastructure. With the proposed reopening just weeks away, The Indian Express reported this week that the Indian authorities had only just brought the road to the same level as on the Chinese side, and the Border Roads Organisation had admitted that it could not widen the single-lane road to two lanes until 2010.
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