La Danta, El Mirador, Guatemala

Only the stone summit of La Danta pokes above the Petén rainforest in northern Guatemala, and the rest of what looks like forested hillside is the pyramid too. Built by the Maya of El Mirador in the Late Preclassic, centuries before Tikal's famous temples, it rises about 72 meters from the forest floor. Guinness lists it as the largest pyramid the Maya ever built, second by volume only to Cholula. Reaching it still means a multi-day jungle trek or a helicopter.