In 1911, Hiram Bingham, famed American explorer, stumbled across a remote Inca city atop a high peak in the Andes. The site was called Machu Picchu--perhaps the most famous ruin in the world. Was it, like Bingham believed, a military fortress or did this glorious ruin have a secret purpose? From the mountains of Peru, host Josh Bernstein will follow in the footsteps of Hiram Bingham. He builds a log bridge across a raging river, examines the stonework at the site, and reviews ancient manuscripts to discover the "true" purpose of Machu Picchu.