As a fan of Colossal Cave Adventure, I’m curious to know whether there’s an active volcano in this cave. Or at least a gold nugget room.

Jonathan Sims catches up with me. Between us and the sunlit passage ahead stands a stalagmite that in profile resembles the paw of a dog.

“The Hand of God would be just too corny,” he says, pointing at the formation. “But the Hand of Dog does nicely, don’t you think?”

He clicks off his headlamp and unweights his gimpy ankle.

“When we first got to the collapsed doline, that skylight up there, I was with another caver and we both had four-year-old sons, so we were experts on dinosaurs, and the whole scene reminded us of something right out of Sir Arthur Conan Doyle’s novel The Lost World,” he says. “When my partner went exploring forward into the sunlight, I told him to ‘watch out for dinosaurs,’ and the name stuck.” —Son Doong cave exploring trips – By Mark Jenkins.