In mid-1998, an Australian pilot flying over South Australia bore witness to a phenomenon that remains a complete mystery even today. In the skies near the town of Marree, the pilot discovered a giant geoglyph depicting an aboriginal man hunting with a stick.
The figure was measured to be 2.6 mi (4.2 km) tall and with a perimeter of 17 mi (28 km), making it the largest geoglyph in the world. Its sheer dimensions require the observer be at an altitude of at least 3280 ft (1000 m) to see it in its entirety.
Unlike other geoglyphs, which researchers are certain were created by ancient civilizations, the one by the town of Marree was created recently.
According to experts, in 1998 the figure was no more than 18 years old, with tremendous efforts invested in its establishment.
Interestingly enough, it seems to have been created in complete secrecy, without anyone noticing. It would have taken a single person 4-8 weeks to make it. There hasn't been a single witness to come forth and reveal its message.
The lines of the figure are about 98 ft (30 m) wide and 11 3/4″ (30 cm) deep, which has led researchers to believe that its creator had used a bulldozer to make the same lines over and over.
The bulldozer would have had to travel 250 mi (400 km) and spend 79 gal (300 L) of fuel to complete the figure.
It has perfect proportions, indicating that the image was made either by an artist or someone with a keen eye. They would have made a sketch first and then used a satellite program to draw the contours onto the terrain.
The precise coordination with geographical longitude and latitude proves that the individual also possessed land surveying skills.
During the first close-up investigation of the Marree Man, researchers found an American flag and a note which was traced to the Branch Davidians cult, whose religious center in Texas was raided by the FBI at that time.
This sparked the initial theory that the geoglyph was created by an American but there were no further leads and the enormous aboriginal depiction remains a mystery.