This week on Jeju: A to Z, Todd Thacker profiles the Yongcheon Cave system. It was discovered in 2005 and it has been the subject of intense scientific study and the source of remarkable discoveries ever since.
On a volcanic island such as Jeju, it’s more than likely that there are many as yet uncovered subterranean formations. In 2005, just such a surprising discovery was made by chance in the northeast of the island.

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Woljeong-ri, Gujwa-eup

Yongcheon Cave, complete with a remarkable underground lake system, was uncovered when an electrical pole was installed in Woljeong-ri, north of the Geomun Oreum lava tube system.

The maintenance workers who returned the next day were shocked to find the pole missing -- swallowed up by a previously unknown cavern.

Scientists were called in and in the following years, after carefully entering and studying the otherwise closed-off system, they found a surprisingly rich set of geological and biological features there.

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800-meter-long underground lake home to new fish species

They found an 800-meter-long underground lake, which in 2010 revealed a previously unknown species of fish measuring four to seven centimeters in length and completely blind.

Though Yongcheon was unknown to modern islanders, it wasn’t always that way. At least since the fifth century, it had been used by humans, as various kinds of earthenware, ironware, animal bones and other evidence of human presence were found. Mysteriously, the original access point, though, is lost.

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Todd Thacker

The scientific importance of this cave cannot be underestimated. In addition to the years of future study and discoveries promised by Yongcheon Cave, some believe that its scientific importance led directly to Jeju earning a place on the UNESCO World Natural Heritage list in 2007.

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wnhcenter.jeju.go.kr

Although Yongcheon Cave is closed to the public, you can get a sense of the site through a carefully replicated diorama and relevant information at the Jeju World Natural Heritage Center in Jocheon-eup. Yongcheon Cave is listed as Natural Monument No. 466.

Todd Thacker KCTV