Aerial photo taken on July 7, 2020 shows ramparts at Dijicheng historical site in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Photo taken on July 7, 2020 shows ramparts at Dijicheng historical site in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Photo taken on July 7, 2020 shows a hotel with local characteristics at Guoyu ancient fortress in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Aerial photo taken on July 7, 2020 shows a view of Dijicheng historical site in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Photo taken on July 7, 2020 shows a hotel with local characteristics at Guoyu ancient fortress in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical c. (Xinhua/Chai Ting)

A tourist strolls at Dijicheng historical site in Yangcheng County, north China's Shanxi Province, July 7, 2020. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Photo taken on July 7, 2020 shows a tunnel at Guoyu ancient fortress in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Photo taken on July 7, 2020 shows buildings at Guoyu ancient fortress in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)

Aerial photo taken on July 7, 2020 shows an outdoor performance stage at Dijicheng historical site in Yangcheng County, north China's Shanxi Province. Built and developed during Ming Dynasty (1368-1644) and Qing Dynasty (1644-1911), Guoyu ancient city and Dijicheng historical site are typical ancient fortress complexes in north China. (Xinhua/Chai Ting)