Natural Reserve

Manjanggul Lava Caves
East of Jeju and about 2.5 km off the coast road from Kimnyong Beach are the caves of Manjangul. The main section of the caves is almost seven km long with a height and width varying from 3 to 20 meters, thus making it the longest known lava tube in the world.

It's damp down there and the temperature rarely rises above a chilly 9C. The cave is well-lit as far as a huge lava pillar.

Hyopchaegul Lava Cave
About 2.5 km south of Hallam on the northwestern side of the island is a group of lava tube caves. The most famous of these Hyopchaegul, is actually a system of several interconnected lava tubes that was only discovered in the 1950s.

Although much shorter than Manjanggul Cave, it is one of the few lava tubes in the world which has stalagmites and stalactites; these are usually only found in limestone caves. In Hyopchaegul the stalactites and stalagmites are caused by large quantities of pulverized shells in the soil above the cave, which have been blown up from the sea shore over thousands of years.