Archaeologists in Jordan have taken high-resolution aerial images of 11 ancient "Big Circles," all but one of which are around 400 meters in diameter. The similarity seems "too close to be a coincidence" said researcher David Kennedy, a professor at the University of Western Australia.
     The Big Circles were built with low stone walls, little more than a metre high, and originally contained no openings. Their purpose is unknown, and archaeologists are unsure when they were built. Analysis of the photographs, as well as artefacts found on the ground, suggest the circles date back at least 2,000 years, but may be much older.
     First spotted by aircraft in the 1920s, little research has focused on these structures.
     In addition to the 11 photographed circles, researchers have identified another similar circle in Jordan, which appears to have been only partially completed. Old satellite imagery also reveals two destroyed circles, one in Jordan and another in Syria.
     Constructed mainly with local rocks, Kennedy thinks a dozen people working hard could potentially complete a Big Circle in a week, however their precise shape would have required planning.
     Archaeologists Graham Philip and Jennie Bradbury, both with Durham University in England, examined a Big Circle they found near Homs in Syria, positioned in such a way that it could give someone standing inside it a "panoramic" view of a basin that would have held crops and settlements. While the circle was "badly damaged" when the researchers found it, they completed their fieldwork before land development completely destroyed the structure.
     Kennedy's 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 radiating spokes); Kites (stone structures that forced animals to run into a kill zone); Pendants (rows of stone cairns aligned with burials); and walls (mysterious structures that meander across the landscape for up to several thousand meters, and have no apparent practical use).

Edited from LiveScience (30 October 2014)