Volunteers from Qinhuangdao of north China's Hebei Province clean up waste along Zhengguanling Great Wall, Aug. 20, 2020. (Xinhua/Wang Yuguo)

Volunteers from Qinhuangdao of north China's Hebei Province clean up waste along Zhengguanling Great Wall, Aug. 20, 2020. (Xinhua/Wang Yuguo)

Volunteers from Qinhuangdao of north China's Hebei Province clean up waste along Zhengguanling Great Wall, Aug. 20, 2020. (Xinhua/Wang Yuguo)

Volunteers from Qinhuangdao of north China's Hebei Province clean up waste along Zhengguanling Great Wall, Aug. 20, 2020. (Xinhua/Wang Yuguo)