Four decades ago, protecting the world's greatest collection of Buddhist art was a cold, lonely job. Stuck in the Gobi Desert, near the northwestern Chinese city of Dunhuang, where the last beacon of the Great Wall rears out of the tawny sands before Central Asia proper begins, young archaeologist Fan Jinshi and her colleagues drank salty water from the nearby Daquan (Big Spring) River that gave them diarrhoea, received newspapers once every 10 days and had to rely on growing their own vegetables. 'In the evenings, we read books by the light of a diesel lamp. It was very lonely on the weekends but we got used to it,' recalls Fan, director of the Dunhuang Academy, a state body set up in 1944 and entrusted with the conservation of the Mogao Grottoes, the fabled 4th-to-13th-century collection of caves painted by devout Buddhist monks. Winter and summer nights alike were long. 'Every now and then we got a movie to watch and even if we'd seen it several times, we watched it. Stuff like The October Revolution and The Tunnel War,' says Fan, naming two communist classics. Today, Fan works out of a smart new building in which the central heating roars throughout Dunhuang's bitterly cold winters, when the average low temperature hits minus-16 degrees Celsius. Waitresses at the local restaurant can return to Dunhuang city, about 25km away, every evening if they want to. Conference rooms, computers and a research block reflect the tremendous artistic, religious, cultural and political significance of Mogao, a collection of 492 painted and 242 unpainted caves hewn into a cliff face beneath the dunes of Rattling Sand Mountain. Just one of many Buddhist cave sites that dot the Silk Road, Mogao is by far the biggest and most famous. Nearly 1,700 years ago, a monk called Lezun was on his way to India to seek enlightenment. With many kilometres of yellow sand and bone-dry, grey-pebbled desert behind him, Lezun still had to cross even-more forbidding stretches of the Taklamakan Desert, in what is today the Xinjiang autonomous region. According to legend, Lezun collapsed, exhausted, in AD366 where Mogao now lies. Lifting his head, he saw a thousand points of light dancing around in the shape of Buddha. Today, scientists believe it was the glitter of mica in the rock; but thrilled with religious fervour, the monk declared the mountain contained Buddha's spirit and dug the first of its caves, in which to pray and meditate. More monks followed and, funded by benefactors, dug more caves into a 1.6km-long cliff face on the east side of the dune-topped mountain. By the time later generations had finished, in 1277, had the paintings that adorned the caves been placed end to end, they would have stretched for an astonishing 10km. Other caves were used as monks' quarters. One thousand years after Lezun first began digging, Mogao had grown to become the grandest repository of Buddhist art in the world. Gloriously colourful paintings executed in delicate, expressive lines showed Buddha's life and death; the benevolence of Guan Yin, the goddess of mercy; mortal lovers trembling with lust; a small child tumbling around in Tang-dynasty (AD618-907) dungarees; and a plump beauty from the AD800s carrying a flower-shaped handbag that could be fashionable today. Mogao is nothing less than an account of 1,000 years of Asian civilisation, with Christianity featured too, reflecting Mogao's place on the east-west artery of the Silk Road. One cave housed a library with tens of thousands of documents in 15 languages, including Uyghur, Tibetan and Sanskrit. Many of the caves are small and cannot comfortably accommodate more than six to eight people at a time. A few are so small the visitor can only stick their head in. A few are huge, such as those containing seated Buddhas. One, Cave 96, contains a 35-metre tall Buddha, the third largest in mainland China. Where monks once worshipped and painted, tourists in their thousands now come to marvel at their work. The caves, in the far west of Gansu province where the Silk Road splits into northern and southern sections, are staggering under the weight of tourist numbers. The caves' paintings, thinner than a sheet of paper and daubed onto clay smeared over stone walls, are flaking and dissolving in the presence of so much humanity. The breath of countless tourists delivers damaging humidity and carbon dioxide into the caves and each time the Sir Run Run Shaw-donated aluminium doors open to let in a tour group, Gobi dust blows in. Damp seeping from the walls accelerates chemical processes that blanch the delicate colours from the paintings, turning the white face of an apsara, or Buddhist angel, brown, and a court lady's pink gown red. Declared a Unesco World Heritage site in 1987, conservationists around the world are unanimous in their assessment: Mogao is a global treasure that must be saved. In a growing number of collaborative projects, various institutes are working aggressively to achieve that goal. 'Dunhuang is ill. Despite that, it stays open. Our job is to extend the life of the patient,' says 68-year-old Fan. 'They've had a hard life, the cave paintings,' says Neville Agnew, group director and a conservation scientist at the Los Angeles-based Getty Conservation Institute (GCI), which is collaborating with the Dunhuang Academy on a model conservation project in Cave 85. Years in the making, the project is nearly finished. 'It's been an enormous challenge technologically because of the difficulty of conserving the paintings. These paintings are not frescoes, where you paint onto wet lime and it dries and is part of the wall. These are wall paintings, which you don't get in Europe. The clay is simply plastered onto the stone walls,' says Agnew. Not only did conservators have to develop new materials to protect the walls, but Dunhuang's location in a seismic zone created special challenges. 'Every time there is a substantial earthquake, chunks fall off. You have to use something to insert into the space between the clay and the wall to fix it. We call it grout and it was specially developed by the GCI and the Dunhuang Academy,' says Agnew. Yet for conservators, it's immensely fulfilling work. 'There's a religious value, an economic value, an informational and a scientific value to the caves. The information is enormous. It's a window on Chinese medieval life,' says Agnew. And conservation must be 'ethos-based'. That means identifying and protecting the cultural, artistic and historic significance of the site. This approach has been enshrined in the Principles for the Conservation of Heritage Sites in China. Drawn up in 2000 by the State Administration of Cultural Heritage with the help of the GCI and the Australian Heritage Commission, the document aims to spread that ethos throughout China, where ancient sites are sometimes viewed as a meal ticket - and often damaged in the process. Tourist visits to Mogao have grown dramatically in recent years. Before the beginning of China's open-door liberalisation policy in 1978, less than 10,000 people each year crossed the pebbly desert plains that surround the caves, traversed the bridge over the Big Spring River, which runs along the base of the mountain, and climbed a series of steps and corridors hewn into the cliff face in the 1960s. About the same time, conservators rerouted the Big Spring 50 metres to the east to stop damp rising into the caves. By 1984, visitor numbers had multiplied tenfold, to 100,000. 'We thought, 'My goodness, so many people, what will we do?' We were afraid it would be harmful to the caves, but we had no choice. And the people kept coming,' says Fan. Last year, nearly half-a-million people came to Mogao. By 2020, according to academy projections, 1.5 million tourists will arrive each year, aided in no small part by a new railway linking Dunhuang with China's national rail network, part of a government plan to open up and develop the west of the country. To the south, the line eventually will connect to the new Lhasa railway. A new station is being built just 15km north of Mogao, a fact that fills Fan with horror. 'It's really frightening to think of that many people.' A tiny woman born in Shanghai, Fan has lived at Mogao since 1963, when she joined the academy fresh from Peking University. Mogao is her life and she is venerated in archaeological circles. Even during the Cultural Revolution, when China convulsed in ideological madness, Fan stayed on at Mogao. In 1975, she was appointed vice-chairman of the academy's revolutionary committee. 'We also made revolution and waved our little red books,' she says, referring to the iconic book of Mao Zedong's sayings. Miracul-ously, for reasons that have never been fully explained, the caves weren't damaged by the Red Guards, who destroyed huge amounts of traditional culture elsewhere. 'Some Red Guards did come here from Dunhuang. We were afraid they'd destroy it, so we said, 'Mogao isn't one of the Four Olds, or a cow devil or snake spirit,'' being any of which made destruction a virtual certainty during the Cultural Revolution. 'We said, 'It's our nation's inheritance.' And they said, 'We've just come to look.'' Fan chuckles. Fan is also a member of the Chinese People's Political Consultative Conference and campaigned against the new railway - or at least tried to have it moved to the other side of Dunhuang city, so it wouldn't spoil the desert landscape around the caves. 'They don't understand that Mogao was part of the surrounding graves and natural environment,' she says. Nor did Dunhuang's tourism and economic-development authorities consult with the academy, one of the biggest employers in town. 'They're thinking of profit,' Fan says. 'They should have held public hearings. They were really stupid ... I told them, if a person can only eat 10 steamed buns, they can only eat 10. They can't eat 15.' Yet, as Fan readily admits, in classic mainland parlance sprung from decades of Marxist dialectics, 'It's a contradiction'. Visitors threaten the caves, but the caves cannot do without visitors, who bring in 40 million yuan a year - the academy's bread and butter. The challenge is to strike a healthy balance between tourism and conservation. 'To resolve this contradiction, we want to reduce the time the tourists stay inside the caves.' To track the impact of tourists, the GCI has chosen two open caves - in the interests of conservation, only about 50, or 10 per cent, of Mogao's caves are open to the public - and two closed ones, and put 'deterioration monitors' in all four. 'It's a management tool - you calculate how many people can be confined in a cave, what is the physical capacity of the cave, what people emit in carbon dioxide and water, interaction with the outside air and what's the impact of all of that,' says Agnew. In a year, the information will be consolidated and a decision made on how much visiting the caves can take. Yet there's a limit even to what the most dedicated archaeological conservator can achieve. 'If you didn't see me for 10 years, you'd be surprised when you saw me again by how much I'd changed, no matter how well I take care of myself,' says Fan. So conservators are turning to computer science for help. Key among the projects to save the works of art is a plan to digitise the contents of every one of them and make the images available to tourists in a visitor centre with an Imax theatre, near Mogao's Japanese-built museum, in the hope of drawing people away from the caves themselves. Images already made are entrancing; statues of Buddha and boddhisatvas loom out at the viewer in 3D, each curve captured in detail as the camera swings around an object. The delicate, ancient colours glow in mint, turquoise, fuchsia, lemon and burgundy; intricate patterns leap out in a way they cannot in the caves, where the lighting is kept dim to protect the paintings. From this kind of material, Fan hopes one day to produce a film. 'Only information that is kept completely and truthfully has its meaning. It's very important for us to have a complete and high-definition record for humankind.' Sarah E. Fraser, associate professor at Northwestern University in Chicago, began a five- year digitisation project in the caves in 1999. Working with the Dunhuang Academy and funded by the Andrew W. Mellon Foundation, the art historian helped digitise 42 caves in a project she dubs 'technology for archaeology', now online at www.ARTstor.org . Digitisation has enabled art historians to see Mogao's paintings in a unified fashion that is stimulating study. 'We're building a semantic web,' or a web of meaning, says Fraser, 'and this material is coming to you. 'It's a project that will disseminate knowledge about this site and integrate it in a way that it wasn't, even in the medieval period, and integrate matter that was removed during the colonial period,' she says, referring to the large amounts of material removed from Mogao in the early 20th century by western explorers such as Hungarian-born Sir Marc Aurel Stein and American Langdon Warner, the model for Steven Spielberg's Indiana Jones character. Digitising the caves involves taking hundreds of pictures of each cave from a camera mounted on parallel rails and splicing the images on a computer. Add the right application and the viewer feels as though they are actually inside the cave. For the first time, paintings can be seen from all angles; sculptures and details formerly hidden in dark corners stand out, imparting new information to scholars. Liu Gang, a soft-spoken former soil scientist from Lanzhou University, is in charge of digitisation at the Dunhuang Academy. Liu pulls up a chair and switches on his computer. A few clicks of the mouse and we are looking at the detail of Cave 61, a seven-by-13-metre cave with a glorious, Tang-dynasty painting of Mount Wutai sporting a rich panoply of human and spiritual life. The entire image was made by splicing together 600 photographs. 'With such a big cave, you can't see the original painting properly. But on the screen, you can,' Liu enthuses. Liu says the academy will record between three and five caves a year, depending on their size. 'It's a question of funding and personnel. If we could get more people it would be quicker.' The most exciting thing for historians and art mavens is that digitisation makes possible the reunification of the paintings with Mogao's documents for the first time since many manuscripts from Cave 17, the Hidden Library Cave, were taken overseas by explorers. Stein was the first to arrive, in 1907, and, for #130, he bought 7,000 scrolls from abbot Wang Yuanlu, who had stumbled on the library seven years earlier. Stein's huge haul included the Diamond Sutra, the world's earliest known printed book, from the year AD868. Most of the manuscripts from the cave can be found in four institutions: the British Library, the Bibliotheque Nationale de France, the Institute of Oriental Studies in St Petersburg and the National Library of China. More explorers followed Stein, carting off artwork to Paris, Dublin, Washington, Tokyo and St Petersburg. Acutely aware that a scattered collection is difficult to study, the British Library began digitising its own collection in 1994 and, in collaboration with the National Library of China, in 2002 launched an online collection (idp.nlc.gov.cn) of 50,000 Silk Road manuscripts in 15 languages. They contain priceless information, not just about Buddhism, but also about Christianity, Taoism and other religions. The scrolls, wooden tablets, slips and books include sutras, rules of living for monks, philosophical discourses and other sacred texts. Since it was an act of faith to copy or pay for the copy of a sacred text, such as the popular Lotus Sutra, there are thousands of these. Yet the manuscripts also contain other material - evidence of the Tibetan occupation of Dunhuang during the 8th and 9th centuries and, intriguingly, proof that Chinese was not as standardised a language as the official dynastic histories claim. There is also a wealth of socio-economic history from the region, since some of the scripts were written on the back of administrative papers taken from the Dunhuang magistracy. These include accounts of a nun's death and to whom she bequeathed her servant, her cow and her land. Others describe remedies for altitude sickness and period pain, and social-club rules (including for women). There are even letters apologising for getting drunk at a dinner party. For Susan Whitfield, head of the British Library's International Dunhuang Project, Mogao is one link in a long chain of Silk Road grottoes, which includes nearby Mount Xumi, Shiergou, Wangmugong and Shuiliandong. Ultimately, she hopes to digitise regional material from the entire first millennium. 'I think there's a general mood now that everyone has to work together to make this amazing resource as accessible as possible,' she says. But she doubts digitising will significantly reduce visitor numbers. 'People want to go and look at the original. They want a feeling that we are connected to the past. Digitisation is never going to replace that.' And the missing manuscripts, many in Whitfield's library, remain a sore point for the Chinese, for whom the removal smacks of colonial theft. Fan has been to London to view some of them. 'I had very mixed feelings,' she recounts over dinner. 'On the one hand, they were well-preserved,' unlike some manuscripts left behind, which were glued onto paper and deteriorate with each unrolling. 'But they are our things. I asked myself, 'Why are they here?'' Fan says she asked the British Museum to lend the scrolls to China. 'They said to me, 'Will you return them? And if you agree to return them, will your people take to the streets and protest?'' It's cold outside and broad plastic strips hanging from the door frame do little to block the wind blowing through the open restaurant entrance. We shiver as we eat. Yet visiting Mogao in winter is probably the smart thing to do. The evening air is icy and the salty waters of Big Spring River are frozen, but in November or March, a person can see Mogao at leisure and in peace; much as the monks must have done more than 1,000 years ago.