The tunnel was constructed in 1969-1971 by the
Republic of China Armed Forces for ships to avoid bad weather and attacks from the
People's Liberation Army in the aftermath of
Second Taiwan Strait Crisis in 1958. It took 820 days for the tunnel to be completed which were mostly done by hand, with some exception of small amount of explosive. Some of the workers lost their lives during the construction process. At that time, the tunnel could harbor 120 small naval vessels but it was badly damaged after a severe typhoon hit the area. After the return of Matsu Islands from military to civilians in 1992, the tunnel was remodeled and opened to the public in 2000. ==Geology==