Tourists visit the Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province, Dec. 16, 2019. (Xinhua/Tao Ming)

Aerial photo taken on Dec. 16, 2019 shows a view of Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province. (Xinhua/Tao Ming)

Aerial photo taken on Dec. 16, 2019 shows a view of Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province. (Xinhua/Tao Ming)

Aerial photo taken on Dec. 16, 2019 shows a view of Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province. (Xinhua/Tao Ming)

Aerial photo taken on Dec. 16, 2019 shows a view of Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province. (Xinhua/Tao Ming)

Photo taken on Dec. 16, 2019 shows a view of Danxia landform, a landscape characterized by reddish sandstone features, in Xinghe Town of Zhidan County, northwest China's Shaanxi Province. (Xinhua/Tao Ming)