The Many Discoveries of Machu Picchu

In 1911 American explorer Hiram Bingham stumbled upon the lost city of Machu Picchu - forgotten since it was abandoned by the Inca centuries before.

That's the story at least, the reality is much more complex. Could he have done it without the help of Peruvians? Was he really the first outsider to get there? And what does it really mean for a ruin to be 'lost'?