One of China's hardest tunnel projects Dazhu Mountain Railway Tunnel, finish on Tuesday after 12 years of work. Part of a railway Dali City and Ruili City in Yunnan Province.

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https://news.cgtn.com/news/2020-04-28/-One-of-China-s-hardest-tunnel-projects-completed-after-12-years-Q47hYkzSw0/index.html ;