On the morning of July 24, 1911, an enterprising lecturer-explorer from Yale University set off in a cold drizzle to investigate rumors of ancient Inca ruins in Peru. The explorer chopped his way through thick jungle, crawled across a "bridge" of slender logs bound together with vines, and crept through underbrush hiding venomous fer-de-lance pit vipers.

Two hours into the hike, the explorer and his two escorts came across a grass-covered hut. A pair of local farmers walked them a short way before handing them over to a small boy. With the boy leading the way, Hiram Bingham stumbled upon one of the greatest archaeological finds of the 20th century—and what was named in 2007 as one of the new seven