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Mountain or Valley? Why It’s Hard to Tell on a Map

If you are standing near a mountain it’s pretty clear you are looking at a mountain. The same goes for a valley; it’s not difficult to comprehend you are near a big hole. But what about when you look at them on a topographical map? Can you identify something sticking up versus something that is below ground?

“Of course!” Then would you be willing to bet your house on whether or not this photo shows a series of plateaus or the Grand Canyon?


Uh…forget your house, would you even be willing to bet a pack of gum on getting it right? Maybe not.

But don’t feel bad, because there’s a very good reason that map is playing tricks on your eyes. And that “Mountain or Valley” optical illusion is the subject of the latest video from the great YouTube channel minutephysics. It has to do with perspective, the sun, and how shadows can fool us into seeing the opposite of what is really there.

Beyond the “shadow” science behind why these photos are so tricky for our brains to read, it’s amazing to learn that almost every map we’ve ever looked at has been intentionally misleading. That’s not how the sun works!

Although in fairness to cartographers everywhere, at least they only lied to us to protect us from our lying eyes.

Oh, and that photo? Flip it around and you’ll see it was actually the Grand Canyon.


Hopefully none of you lost your house because of some tricky shadows.

What other optical illusions would you like to have explained by minutephysics? We want to see your best suggestions in our comments below.

Images: minutephysics

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