A tourist takes photos of the scenery in Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Ma Ning)

People enjoy the scenery of Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Ma Ning)

People enjoy the scenery of Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Chen Bin)

Aerial photo taken on June 19, 2019 shows the Guan'egou National Forest Park shrouded in fog in Dangchang County of Longnan City, northwest China's Gansu Province. (Xinhua/Chen Bin)

People enjoy the scenery of Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Ma Ning)

Aerial photo taken on June 19, 2019 shows the Guan'egou National Forest Park shrouded in fog in Dangchang County of Longnan City, northwest China's Gansu Province. (Xinhua/Chen Bin)

People enjoy the scenery of Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Chen Bin)

A tourist poses for photo with the scenery of Guan'egou National Forest Park in Dangchang County of Longnan City, northwest China's Gansu Province, June 19, 2019. (Xinhua/Ma Ning)

Aerial photo taken on June 19, 2019 shows the Guan'egou National Forest Park shrouded in fog in Dangchang County of Longnan City, northwest China's Gansu Province. (Xinhua/Chen Bin)