Aerial photo taken on June 13, 2018 shows the Tianchi Lake in Wenxian County, northwest China's Gansu Province. The Wenxian Tianchi Lake is located on the Tianwei Mountain in Longnan City of Gansu. (Xinhua/Zhang Meng)

Photo taken on June 13, 2018 shows the Tianchi Lake in Wenxian County, northwest China's Gansu Province. The Wenxian Tianchi Lake is located on the Tianwei Mountain in Longnan City of Gansu. (Xinhua/Li Xiao)

Aerial photo taken on June 13, 2018 shows the Tianchi Lake in Wenxian County, northwest China's Gansu Province. The Wenxian Tianchi Lake is located on the Tianwei Mountain in Longnan City of Gansu. (Xinhua/Zhang Meng)