Giant circular structures known as the "Big Circles," whose sizes were mostly about 1,300 feet in diameter, are scattered across the Middle East.

The vast rings, which can only be seen in aerial and satellite views, were first discovered in the 1920s, but surveys conducted in 1930, 1953 and 2002 have unraveled more information about these strange structures, including their shape, size and location.

The circles were constructed using low stone walls and they originally did not have openings, so people would need to hop over the stone walls to get inside. Much about the circles, however, remains a mystery. For one, it isn't clear when these structures were built.

A group of archeologists recently took high-resolution aerial images of 11 of these structures, unraveling details that could shed light on some of the mysteries of the Big Circles. An analysis of the images and artifacts suggests that the ancient circles were at least 2,000 years old albeit scientists said that they could be much older. It is possible that these structures were made in prehistoric times before man even learned to write.

The purpose of the structures also remains unknown. David Kennedy from the University of Western Australia leads the Aerial Archaeology in Jordan Project (AAJ) and says that it isn't likely that the structures were used as corrals because of the low stone walls. The circles did not also have structures that would have helped in maintaining an animal herd; animal corrals also do not need to have such a precise circular shape.

Although the circles have three cairns or piles of stones on its edges, which were possibly used for burial purposes, Kennedy thinks that these structures were built later.

"The landscape of the Middle East is thickly strewn with circular or sub-circular stone-built structures," Kennedy said. "Most are crude circles, but many are clearly intended to be geometrically precise, although often slightly distorted."

While there are other smaller stone circles in the Middle East, the 11 photographed circles stand out from the rest because of their ancient age and size. In addition to the 11 stone circles that had been photographed, the researchers also identified a similar circle in Jordan that looks like it was only partially completed.

Old satellite images also showed one circle in Jordan, which was destroyed several decades ago, and another in Syria that was destroyed over the last decade.

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