I've seen them, and I'm sure you have, too. Rocks are stacked and balanced in various formations on hiking trails, beaches, and in deserts. There's actually something artful about it and very Zen.

All along the Llano River, rock towers rise like tiny skyscrapers engineered by Mother Nature. Knobby rocks the size of hiking boots balance like ballerinas on smooth, egg-size stones. Some bend into ...