The volcanic island of Jeju, located 130 kilometers from the southern coast of the Korean Peninsula, has an extensive system of lava tubes. These natural conduits through which magma once flowed are now empty caves that are some of the largest in the world. These caves, apart from providing opportunities for scientific research, are popular tourist destinations.

The most impressive is the Geomunoreum Lava Tube System formed by the flow of basaltic lava when the Geomunoreum volcano erupted some 300 - 200 thousand years ago. The volcano has an elevation of 456 meters and lava flowed down to the coastline 13 km away, and while doing so, created numerous lava tubes. The Manjanggul Lava Tube represents the largest cave in this system. It stretches for 8,928 meters and its passages are up to 30 meters high and 23 meters wide.

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