Tourists visit the Badaling Great Wall in Beijing, capital of China, June 10, 2018. The Badaling Great Wall received more than 20,000 visitors per day recently.[Photo/Xinhua]

Tourists visit the Badaling Great Wall in Beijing, capital of China, June 10, 2018. The Badaling Great Wall received more than 20,000 visitors per day recently.[Photo/Xinhua]

Tourists visit the Badaling Great Wall in Beijing, capital of China, June 10, 2018. The Badaling Great Wall received more than 20,000 visitors per day recently.[Photo/Xinhua]

Tourists visit the Badaling Great Wall in Beijing, capital of China, June 10, 2018. The Badaling Great Wall received more than 20,000 visitors per day recently.[Photo/Xinhua]