Photo taken on July 27, 2013 shows a chain of colorful undulating hills at the Danxia Scenic Area in Zhangye City, northwest China's Gansu Province. Danxia, which means "rosy cloud", is a special landform formed from reddish sandstone that has been eroded over time into a series of mountains surrounded by curvaceous cliffs and many unusual rock formations. (Xinhua/Wang Song)