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A look up at the bottom of Gouffre de Padirac, a cave system more than 100 meters under the surface. The ceiling collapsed long before humans discovered it, creating a sinkhole 75
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:max_bytes(150000):strip_icc()/mammoth-caves-national-park-kentucky-KYCAVES0619-d76d0fc6d4384b549cae5ceb87a7c9fa.jpg "Kentucky Is Home to the World's Longest Known Cave System — Here's How to Explore It")
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