I saw an article today linked from The Debris Field Blog on the Costa Rican stone balls. It's a translated article, so it doesn't always make the most sense grammatically, but you'll get the idea.

These stone balls, as seen in the image above taken from the article, have been found all over the place, on hills, in the jungle, and they're always amazingly spherical. I always wondered if they were found in the locations at which they were placed, and then mapped out, if you'd find a correlation to constellations, or some other noticeable pattern. Unfortunately, over the past couple of decades it became fashionable for upper-class citizens to use them as lawn ornaments, and most of them have been moved from their original resting places by now.