The Manjanggul Lava Tube is a natural lava tube located on Jeju Island, South Korea. It was formed by volcanic activity around 300,000 to 200,000 years ago and stretches approximately 7.4 kilometers in length, although only a portion is open to the public. The tube features impressive lava formations, including stalactites and lava columns. This geological wonder is part of the Jeju Volcanic Island and Lava Tubes UNESCO World Heritage Site. Visitors can explore a 1-kilometer section of the tube, which showcases the unique volcanic landscape and provides insight into the island's geological history.