Jeju Volcanic Island is a UNESCO World Heritage site located in South Korea. It is known for its stunning volcanic landscapes, including Hallasan, the highest mountain in South Korea, and numerous craters and lava formations. The island was formed by volcanic activity millions of years ago, resulting in unique geological features and diverse ecosystems. The lava tubes on Jeju are natural tunnels formed by flowing lava that cooled and solidified on the surface while the molten rock continued to flow beneath. These tubes, such as Manjanggul, are some of the longest and best-preserved in the world, showcasing fascinating formations like stalactites and lava columns.