Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province. (Photos: Xinhua/Mu Yu)

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.

Aerial photo taken on Aug. 25, 2020 shows clouds over a section of the Great Wall in Qianxi County, north China's Hebei Province.