A boy plays on salt pans in Markam County, southwest China's Tibet Autonomous Region, March 21, 2015. Markam county, with rich salt resources, has more than 3,000 salt pans to evaporate brine in the sun with an ancestral technique since Tang Dynasty (618-907AD), which is also the oldest method of salt production. This salt evaporation method was listed as one of China's National Intangible Cultural Heritage in 2009. (Xinhua/Zhang Xiaohua)