Barkol singing sand dune is surrounded by green in Hami prefecture in China’s Xinjiang Uygur autonomous region on August 5, 2011. The dune is said to “sing” as it emits sound that may be caused by wind passing over the dune or by people walking on the sand. Barkol dune is a natural wonder of the region and attracts large groups of tourists from around the world. [Photo/Xinhua]