A Mayan city was discovered in the Mexican jungle after being hidden for more than 1,000 years. Airborne laser mapping allowed researchers to peer through the dense canopy to detect the 37-acre settlement on the Yucatán peninsula; the team then hacked a three-mile path through the jungle with machetes to reach the site, which features a 43-foot-tall pyramid temple.

The Late Classic period, between around 250AD and 900AD, was the height of Mayan civilization: Vast, intricately designed buildings reveal advanced astronomical and mathematical understanding. The Mayan population, spread across much of what is now Mexico and Central America, may have reached 16 million. But it mysteriously collapsed within a century, possibly as a result of changing climatic conditions.