In 1998, a charter pilot flying over the remote South Australian outback looked down and saw a 2.7-kilometer-tall man carved into the earth. It wasn't there a month earlier, no one saw it being made, and decades later no one knows who did it.

This episode investigates the Marree Man, a colossal geoglyph that appeared in roughly two weeks using earth-moving machinery and advanced GPS. We follow the bizarre trail of anonymous faxes, buried jars, and American red herrings, the explosive native title clash it ignited, and why it may be the last planetary-scale mystery humanity ever allows to be created.

• Satellite imagery proving the 28-kilometer figure was completed in about 14 days
• Why 1998 GPS scrambling meant the creator needed military-grade or differential GPS
• The strange clues: US spellings, a buried jar, a dedi ...