峰牙－己榜国家公园中的韩松洞，越南 Sơn Đoòng cave in Phong Nha-Kẻ Bàng National Park, Vietnam (© David A Knight/Shutterstock)

峰牙－己榜国家公园中的韩松洞，越南 Sơn Đoòng cave in Phong Nha-Kẻ Bàng National Park, Vietnam (© David A Knight/Shutterstock)

A universe underground

When Vietnamese farmer Hồ Khanh stumbled upon this cave in 1991, it was immediately clear the gaping mouth led to a huge, dark, untouched chamber, complete with a free-flowing underground river. What couldn't have been clear to him then was that this cave, now known as Sơn Đoòng, is by far the world's largest in volume.

Lacking gear to explore the cave further, Khanh could only wander back home and tell friends about his discovery. But he was unable to retrace his steps to the cavern, his tracks engulfed by the jungle. Relegated to rumor, the cave went unexplored for almost two decades until a visiting team of British cavers caught wind of Khanh's tale. In 2009, Khanh led them to Sơn Đoòng after a long search, and explorations commenced that found the cave was vast beyond anyone's expectations.

Sơn Đoòng is over 1.5 billion cubic feet in volume, with its main chamber 650 feet high, almost 500 feet wide, and stretching more than 3 miles, large enough to fly a Boeing 747 through—but look out for the 15-story stalagmites. One of the cave's massive dolines—sunken, sun-exposed sections like the one seen here—hosts an entire rainforest ecosystem. And that's just what we know so far: Cave divers have yet to fully explore Sơn Đoòng's subterranean river, and vast passages found as recently as 2019 have only added to what's known of the cave's enormity.

地下的宇宙

1991年，当越南农民HồKhanh偶然发现了这个洞穴时，人们立刻清楚地看到，张开的洞口嘴通向一个巨大的、黑暗的、未被触及的洞穴，里面有一条自由流动的地下河。当时他不清楚的是，这个洞穴，现在被称为SơnĐoòng，是迄今为止世界上最大的洞穴。

由于缺乏进一步探索洞穴的装备，卡恩只能漫步回家，告诉朋友他的发现。但他无法回到洞穴，他的足迹被丛林吞噬。由于流言蜚语的影响，这个洞穴在近20年的时间里一直未被发现，直到一队英国探洞者闻到了卡恩的故事。2009年，Khanh带领他们经过长时间的搜寻，来到了SơnĐoòng，开始了探险，发现这个洞穴的面积超出了任何人的预期。

SơnĐoòng的体积超过15亿立方英尺，其主舱室高650英尺，宽近500英尺，长度超过3英里，足以让一架波音747飞机通过，但要注意15层楼高的石笋。洞穴中一条巨大的低谷下陷，暴露在阳光下，就像这里看到的一样，这里有一个完整的雨林生态系统。而这正是我们目前所知道的：洞穴潜水员还没有完全探索sơnĐoòng的地下河，而最近在2019年发现的巨大通道只是增加了人们所知的洞穴的巨大性。