They might be seen as paranormal phenomena, but these creations are human-made, produced either as pranks or with a clear concern for aesthetics.
The one shown here takes the form of a triple Julia-set fractal, discovered in 1996 at Windmill Hill, Avebury, in Wiltshire (United Kingdom). Die-hard enthusiasts have even noticed eleven circles on one spiral, eleven on another and twelve on the third… But 11 + 11 + 12 = 34, one of the Fibonacci numbers! From there, it is only a short step to believing that the Devil had a hand in it, as in the earliest account of a crop circle, from 1678…
