Crouched on the floor in the mud in one of the biggest cave chambers in China, one of the biggest in the world, we can hear nothing but our breathing and the drip, drip of distant water.

oozy mud.” “We can’t go over it, we can’t go under it,” they muse. The solution they land on: go through it. (Spoiler: They find the bear in a cave and run away—not at all hiker protocol.) ...

mud-caked ropes that help guide us through myriad passages known in caving argot as “squeezes,” “meanders,” and “shafts.” These passages have already been mapped, but as we crawl up ...