One of the first things visitors to The Silk Road: Treasures from Xinjiang exhibition notice is the outstanding condition of the artefacts. We can thank Xinjiang's climate for that - its desert region is one of the driest and saltiest places on the planet and the sand has preserved the pieces for centuries (the oldest item on display is nearly 3,000 years old). 'The organic relics, like silk, paper, wood and mummies, are so well-preserved that their original colours and writing can still be clearly seen,' says Brian Lam Kwok-fai, curator of the Heritage Museum The Cherchen Man dates from 800BC. His corpse is so well preserved that his eyebrows, fingernails, beard and braids are all intact; and his burial garments surprisingly vivid. The museum has taken steps to ensure that the treasures remain in top condition. Tailor-made showcases with humidity regulators have been installed to prevent deterioration. The main theme of the exhibition - which includes ancient bronze wares, Persian coins, silk paintings, gold plaques and documents - is the earliest days of east-west relations. 'There are significant archaeological discoveries and new relics among our exhibits,' says Lam. 'But they all share the same theme: to demonstrate in detail the religions, cultural practices and daily lives of our ancestors living in the prosperous communication hub to the west. 'You can see cultural practices and religions from various civilizations in our selected exhibits. Traces of Buddhism, Zoroastrianism and even a branch of Christianity can be found in the ornaments, bronze wares and funeral items. The cultural exchange back then was intense.' The exhibition includes a Manichaean letter written in Sogdian, an Iranian language. Manichaeism was founded in Persia in the third century. 'Historians believe that Manichaeism later spread to the mainland China along the trading route,' Lam says. Other items of note include textiles - particularly felt and wool clothing from the State period (770-221BC) - the designs of which point to a clear western influence. 'The motif of these hand-printed fabrics is often winged beasts, which demonstrates a clear influence from the west,' Lam says. For all that travelling back and forth, official documentation was inevitable, and the museum has what must be one of the world's oldest passports. The guosuo, or travel permit, (AD732) was recovered from the oasis city of Turpan and contains a detailed declaration of the traveller's servants, donkeys and intentions on entering the city. 'The guosuo 1,200 years ago is basically the passport we have today,' says Lam. 'They had to get a specific chop - still clearly visible on the paper - at the entrance of each city before they could enter.'