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Voyage to Our Hollow Earth:
"Would you be interested in a once-in-a-lifetime chance to discover Our Hollow Earth first hand? If so, we invite you to join us for an expedition to the North Pole with Steve Currey, one of the leading river explorers in the world!"

Hey, you never know. Osama might be there. Or Saddam. Or maybe that's where he hid the WMD.