First discovered in the 1920s at the dawning of the era of aerial photographs, these mysterious stone structures throughout the Middle East are called simply "the Big Circles" by archaeologists. We now know roughly how old they are, but we still don't know who made them, and why there are so many.
What you're looking at above is J2, a circle that's 1,280 feet in diameter, located in Jordan. It looks impressive from the air, but down on the ground it appears to be a toppled pile of stones.
Over at LiveScience, Owen Jarus explains that a recent aerial survey by archaeologists in Jordan has revealed 11 of these structures, most of them bigger than 1,000 feet in diameter. They are at least 2,000 years old, but may be thousands of years older, perhaps from a time before humans had invented writing. Some of the circles have also been found in Syria, though most are hard to locate because their shape isn't obvious from the ground.
The circles don't seem to have any openings, but archaeologists believe they were only a few feet high when they were built. Some of them are located next to cairns, or rock piles, which may have served a ceremonial purpose. What's clear is that these megastructures were part of a building practice that was common throughout the Levant area. Stones were piled and shaped to signify everything from city boundaries to spiritual practices.
Archaeologist David Kennedy, who worked on the aerial survey, says that the circles are similar enough that they were probably built by communities that shared some cultural traditions.
While the purpose of the Big Circles remains unknown, the research by Kennedy and his team shows that the creations were part of a landscape rich in stone structures.
His team has found thousands of stone structures in Jordan and the broader Middle East. They come in a variety of shapes, including "Wheels" (circular structures with spokes radiating out); Kites (stone structures that forced animals to run into a kill zone); Pendants (lines of stone cairns that run from burials); and walls (mysterious structures that meander across the landscape for more than a mile — or up to several thousand meters — and have no apparent practical use).
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Images by David L. Kennedy, via Aerial Photographic Archive for Archaeology in the Middle East