There was a time, before football and rock'n'roll, when explorers were the A-listers of their day. Death-defying antics and tales of daring made them the stuff of legend: names like Columbus, Raleigh, and Cook, who sailed off over the horizon to discover new lands and bring home treasures unimaginable to those sitting at home in dark, damp Europe.   Intrepid explorers they may have been, but ‘great' might be pushing it. Across the seven seas, they spilled blood and spread disease. They enabled the destruction of civilisations and the growth of slavery.  And many of their ‘discoveries' weren't quite what you'd think...   Christopher Columbus - who stumbled across the Americas, but insisted he was in Asia.   Sir Walter Raleigh - who didn't discover potatoes, tobacco, or El Dorado, but hustled his way into the history books.Captain James Cook - who failed in his search for Antarctica but charted a third of the world map along the way.   James will discover what really happened - and how. There'll be hands-on experiments, technological wonders, and plenty of messing about in boats, as he explores the science, engineering, and sheer stubbornness that allowed these extraordinary explorers to sail to every corner of the earth.