Summary In the jungles of southern Mexico, a rancher is out looking for an escaped cow when he comes across a cave mouth that leads twenty feet into the earth. Curious, he climbs down and is shocked to discover dozens of skulls and bones lying in piles on the cave floor. What could have happened here? On the plains of central Bohol, a Philippine island, a group of researchers exploring the area come across a strange sight - littering the landscape are countless perfectly conical shaped grass covered domes extending as far as the eye can see. What could they be? On Kauai Island, Hawaii, archaeologists investigating a steep cliff come across dozens of carved stone figures that look like nothing else they have previously found in Hawaii. The sculptures have disproportionately big heads with bulged eyes and flattened noses. Who made these and why? Along the Tambopata River in the rainforest of southeastern Peru, a scientist notices a bizarre-shaped structure attached to a blue tarp above him - tiny white parallel silk strands circled around a stalk-looking cone. Measuring only 2 centimeters across, it must be the work of an insect, but it's unlike anything he's ever encountered. What is this strange formation?

• Documentary