Digging for the Truth Season 3 Episode 6 Machu Picchu: Lost City of the Inca ( Air Date 2007-03-05 ) Genre Documentary, Mystery category. Overview "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?".