Ruins of the Yumen Pass is seen in Dunhuang, northwest China's Gansu Province, Sept. 8, 2016. As an important stop on the ancient Silk Road, Dunhuang is known for the Mogao caves, Yumen Pass, etc. This year, the Silk Road (Dunhuang) International Culture Expo will be held from Sept. 20 to Oct. 10. (Xinhua/Chen Bin)

The Crescent Spring and Singing Sand Dune scenic area is seen in Dunhuang, northwest China's Gansu Province, Sept. 9, 2016. As an important stop on the ancient Silk Road, Dunhuang is known for the Mogao caves, Yumen Pass, etc. This year, the Silk Road (Dunhuang) International Culture Expo will be held from Sept. 20 to Oct. 10. (Xinhua/Chen Bin)

Dunhuang Silk Road International Convention and Expo Center is seen in Dunhuang, northwest China's Gansu Province, Sept. 7, 2016. As an important stop on the ancient Silk Road, Dunhuang is known for the Mogao caves, Yumen Pass, etc. This year, the Silk Road (Dunhuang) International Culture Expo will be held from Sept. 20 to Oct. 10. (Xinhua/Chen Bin)

The Singing Sand Dune scenic area is seen in Dunhuang, northwest China's Gansu Province, Sept. 6, 2016. As an important stop on the ancient Silk Road, Dunhuang is known for the Mogao caves, Yumen Pass, etc. This year, the Silk Road (Dunhuang) International Culture Expo will be held from Sept. 20 to Oct. 10. (Xinhua/Chen Bin)

A road runs through the Yadan landscape in Dunhuang, northwest China's Gansu Province, Sept. 8, 2016. As an important stop on the ancient Silk Road, Dunhuang is known for the Mogao caves, Yumen Pass, etc. This year, the Silk Road (Dunhuang) International Culture Expo will be held from Sept. 20 to Oct. 10. (Xinhua/Chen Bin)Source: english.qianlong.com