They stretch from Syria to Saudi Arabia, can be seen from the air but not the ground, and are virtually unknown to the public. Referred to by archaeologists as 'wheels,' these stone structures have a wide variety of designs - a common one being a circle with spokes radiating inside. Researchers believe that they date back at least 2,000 years. They are often found on lava fields, and range from 25 to 70 metres across.
     New research by David Kennedy - professor of classics and ancient history at the University of Western Australia - reveals that these wheels form part of a variety of stone landscapes; including 'kites' (for funnelling herds of animals), 'pendants' (lines of stone cairns that run from burials), and walls that meander across the landscape for up to a hundred metres or more. Some of the wheels are found in isolation while others are clustered together. At one location, near the Azraq Oasis (Jordan), hundreds can be found clustered into a dozen groups.
     Kennedy became fascinated by these structures when, as a student, he read accounts of Royal Air Force pilots flying over them in the 1920s on airmail routes across Jordan. In Saudi Arabia, Kennedy's team has found quite different wheel styles; some are rectangular, others are circular but contain two spokes forming a bar often aligned in the direction that the sun rises and sets. The wheels in Jordan and Syria, on the other hand, have numerous spokes and do not seem to be aligned with any astronomical phenomena.
     Cairns are often associated with the 'wheels'. Sometimes they circle the perimeter of the wheel, other times they are in among the spokes. The researchers have noted that the 'wheels' are often found on top of 'kites' - which date as far back as 9,000 years - but never the other way around.

Edited from Live Science (14 September 2011)