Our brains are pretty good at physics. For instance, you can watch somebody kick a soccer ball in front of you, and you can run to the spot where you and that soccer ball will intersect, taking into consideration the speed of both you and the ball — so smart! Not only that, we can look at one object balancing on another and tell how sturdy it is without so much as touching it.

But sometimes our brains make uneducated mathematical guesses, and one of these is Kummakivi, the balancing rock in Ruokolahti, Finland. If it was up to your brain, Kummakivi — which means "strange rock" in Finnish — wouldn't exist. It's a boulder resting on a lump of rock in a position that, to our monkey engineer brains, appears impossible, or at least dicey. Extremely slap-dash and temporary work, at best. And yet Kummakivi sits quietly in its Scandinavian forest, racking up the centuries. Millennia, even.