The massive Sn ong Cave is a natural feature unlike any other on Earth, located deep among the remote jungles of central Vietnam's Phong Nha-K Bàng National Park, a UNESCO world heritage site. The Google Doodle for today honours this massive cavern, which was found on this day in 2009. Expert geologists believe the Sn ong (Vietnamese for "Mountain River") Cave was constructed between two and five million years ago, aeons before local farmer Ho Khanh unexpectedly discovered its massive entrance in 1990. The cave remained unaltered until 2008, when Khanh retraced his steps back to the cave's foggy entrance, and until 2009, when he retraced his steps back to the cave's misty entrance with Howard and Deb Limbert of the British Cave Research Association. The cave's first formal survey was undertaken by the brave speleologists, who decided that it was the world's largest cave. Scientists discovered a plethora of record-breaking geological formations inside Sn ong's undisturbed inner chambers (huge enough to house an entire city block of 40-story buildings!) including the world's largest limestone pearls and tallest stalagmite. Giant sinkholes deeper down in the cave allow sunlight and rain to nurture two pristine jungle ecosystems that are home to flying foxes, the world's only underground monkeys, and eyeless white fish. One of these lush jungles is so large that it even has its own weather system! In 2019, a group of British divers discovered an underwater tunnel connecting Sn ong to another cave, adding an additional 5.6 million cubic feet to the cave's already massive volume of 1.35 billion cubic feet. Here's to a natural wonder that should be on everyone's trip wish list!