One of the most significant geological finds in recent exploration—the discovery of Vietnam’s Hang Son Doong, the world’s largest cave—almost never happened. Circa 1990 farmer Ho Khanh stumbled across an entrance and a limestone overhang in the thick jungle of Phong Nha-Ke Bang National Park. The distant noise of rushing water caught his attention, but he thought no more of it. Given the thick, almost impassable, Vietnamese jungle, the farmer’s trail was lost in any case, and he did not try to find his way back. For about 18 years, Son Doong’s existence was seemingly destined to remain a secret, but eventually, he would mention his find to a curious couple from the British Cave Research Association (BRCA).
Ho Khanh wasn’t alone in his close encounters with the monster cave. Howard and Deb Limbert, members of the BRCA, have been exploring the area for decades, and in 1994 the pair encountered two caves. First they explored Hang Thung, a cave downstream from Son Doong, where an underground river emerged. Then within a couple of weeks, they ventured into Hang En, a large cave upstream from Son Doong, whose river disappears into boulders. It was clear that a gap of some five kilo-meters between these spots could be a cave carved by the same water flow.
Son Doong turned out to be immense. Reportedly large enough to hold a city block of skyscrapers, it seems otherworldly. Making the space even more impressive