New evidence might finally identify the hiding place of the billion-dollar Nazi gold train; a discovery of a long-lost settlement rewrites the history of the Vikings in North America; a blood-red river in Siberia points to catastrophic pollution.

An ancient man-made volcano might reveal buried treasure and bloody human sacrifice; when NASA discovers a strange pattern in the Arctic ice, experts investigate if it has alien origins; a mystery in the Sahara might have a sinister explanation.