Manjanggul Lava Tube

This guide to Manjanggul in Jeju follows Bu Jong-hyu, a schoolteacher who tied a rope around his waist in 1946 and led his students into an unmapped hole near their village, letting out rope as passage after passage kept unrolling ahead of him. It traces how the tube itself formed, as molten rock draining beneath its own cooling crust hollowed out one of the longest lava tunnels on earth. It took him a full year, from 1946 into 1947, before the rope finally ran out at a third opening in the ground.