Stone Spheres

http://commons.wikimedia.org/wiki/Image:Stone_sphere.jpg
Image: Wikimedia Commons

Since the 1930s, hundreds of stone spheres have been found in Costa Rica. They range from a few centimeters to more than 2 meters in diameter and weigh up to 16 tons.

No one knows who made them or why, but they’re old — some date to 200 B.C.