Archaeologists have snapped aerial photos of ancient stone circles as part of an ongoing effort to figure out why the structures exist, LiveScience reports. The images (taken in Jordan and viewable here) show that 10 of the 11 structures are roughly 1,300 feet in diameter, but their purpose remains a mystery. What experts do know: The so-called "Big Circles" date back 2,000 years or more, have stone walls that were likely too low to function as corrals, and included no openings. The structures are also crude attempts at circles, indicating that an architect marked the shapes by walking a rope from the center, but messed up the circle where the ground was uneven. What's more, one circle has three rock piles (or "cairns") on its edge that might have functioned as burial sites.
But researcher David Kennedy says he believes that "the cairns [were built] later, when the enclosure was no longer significant." Many stone circles exist in the Middle East, including one in Syria near Homs that has been totally destroyed. According to a 2010 research paper, it was built on a spot that gave anyone inside it a perfect view of a basin full of settlements and crops. Other stone structures around the Middle East come in various shapes, including walls that wander across landscapes, "kites" that directed animals into a killing zone, and "wheels" that have spokes sticking out of a circle. As for the Big Circles, Kennedy says the next step is to excavate them, Science Alert reports. See a YouTube video on the circle hunt, or read about a city founded by Genghis Khan's descendants. (Read more archaeology stories.)