Charter pilot Trevor Wright was flying over South Australia in 1998 when he discovered something astonishing: the colossal image of a human being, 4.2 kilometers long, carved into the earth.

It must have taken weeks to etch the figure into the arid soil with a tractor and a plough. Even planning the work probably required aerial photography or satellite imagery, surveying skill, and GPS technology.

But no one knows who created the figure, when, or why.