The Manjanggul Lava Tube is located in Gimnyeong-ri, Gujwaeup, Jeju City. At 23m high, 30m high and 8.928km long, it is the 12th-longest lava tube in the world[1] and the second longest on Jeju island.[2] It is regarded as having significant scientific and heritage value, owing to its excellent condition of preservation despite its age of formation (about 300,000 to 200,000 years ago).