Crop circles are another of these mysterious phenomena that intrigue scientists, mystics, and the general public alike because their appearance is unexplained.
Crop circles have been around for a while, but became most popular when a number appeared in England in the 1970s and 1980s. New crop circles have appeared every spring and summer. A crop circle is an area of a field, usually planted with wheat, corn or other such crops, which has been flattened in sections that form patterns when viewed from the air. These patterns are large, complex, precisely made, and generally appear overnight without anyone seeing them being made. This has, quite naturally, led to speculation about their origin being paranormal at least if not alien, made by extraterrestrials visiting us in their UFOs.
Image of Crop Circle near Chartley Manor Farm from Wikimedia Commons.