Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)

Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)

Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)

Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)

Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)

Photo taken on June 3, 2020 shows a section of the Jiankou Great Wall in Huairou District of Beijing, capital of China. (Photo by Chen Zhonghao/Xinhua)