LIENCHIANG COUNTY (Taiwan News) – The Beihai Tunnels on the outlying Matsu Islands were kept a strict secret until the 2000s, though before that, local tour guide Lin Chia-chun (林家君) said a soldier once snuck her in.

The Matsu Islands are formally known as Lienchiang County and were part of China's Fujian Province (福建省). After 1949 Taiwan heavily fortified the islands with hundreds of tunnels against the Chinese communists.

The Beihai Tunnels are one of them, and Lin described how the 700-meter-long, 18-meter-tall, and 10-meter-wide subterranean structure was dug almost entirely by hand. No longer secret, the Beihai Tunnels are now a tourist attraction where visitors can take guided tours on canoes, float down the tunnels' waterways and learn about the location’s history.

Watch the Taiwan News feature on Matsu's Beihai Tunnels on YouTube.

Lin told Taiwan News that soldiers worked 24 hours a day in shifts to excavate the site, which went on to be used for secretly transporting goods from Taiwan to the islands. She said an unknown number of soldiers died digging out the tunnels – a dangerous and arduous task that involved explosives, pickaxes, and wheelbarrows. 

When soldiers who worked on the tunnels come back to visit, Lin said she waives the entrance fee. The people still revere the soldiers, and despite the hardships that came with their prolonged presence on the island, they also remember the economic prosperity they brought. 

The tunnels offer more than just historical sights and engineering marvels. Sheltered from the elements, the tunnels also provide a unique environment for wildlife. 

At certain times of the year, visitors can also view the “Blue Tears” phenomenon – bioluminescent sea algae that turns the waters around Matsu a neon blue. “Because the water temperature inside the tunnel is constant, and there is no light pollution in here, it becomes a very important habitat for the ‘Blue Tears.'” Lin said.