Around the world, ancient cultures have constructed mysterious geoglyphs — large motifs etched into the landscape — which often can only be viewed from the air. Because these features were created at a time before air travel was possible, their existence has led to speculation about their origins. Who was the intended audience for these geoglyphs? Who built them? What was their purpose?
Here's our list of 10 of the biggest, most mysterious features that can only be spied from the air. (Text: Bryan Nelson)