Jeju Island is formed by lava flow streams with the Mt. Halla in the center. The Mt. Halla‘s crater or other parasitic volcano produced lava flows creating lava plateau in this area. There are one thousand volcano caves in the world, and 50% of them are located in the west coast of United States. There are 186 volcano caves in Italy, 100 in Mt. Fuji, Japan, and 70 in Jeju Island. Jeju Island‘s east-west axis four sides are world-renown volcano zones with basalt strata that feature low viscosity and fluidity.