The lowest point in China is an unlikely place for a wine industry to be based. It's possibly the hottest and driest place in the country. It also gets cold, down as low as -24.4C. And it's smack in the middle of the great sandy desert which, under various names, stretches right across Central Asia. But there's evidence grapes have been grown in this inhospitable place for millennia, supported by an intricate underground irrigation developed by the Uighur people.