Hawaiian-born, Yale-educated Hiram Bingham was determined to make a name for himself as an explorer. At the beginning of the 20th Century, when the last empty spaces on the globe were fast disappearing, he decided to climb South America's highest mountain and discover the legendary last refuge of the Incas after the Conquistadors' invasion. In the end, the mountain he scaled turned out to be only the second-highest. And the lost city in the clouds he discovered was not the Inca refuge, but an administrative centre: the fabulous Machu Picchu, still one of the greatest tourist magnets in the world. Today's archaeologists can at last explain how it was built, with astonishing precision, 4,000 meters up on the mountain-tops - a sophisticated canal system was constructed to prevent it being washed away. And as if to emphasize that even today this is an extreme region, in January 2010 hundreds of visitors had to be rescued from Machu Picchu by helicopter in a days-long ordeal, after rockfalls and heavy rain cut off their return journey.