So, of course that led to the article about Crop Circles. The term just dates back to the 1980s, and apparently it's pretty easy to explain them all as creations by human pranksters, but some people still insist that they are related to extraterrestrials and UFOs, the mythical beings of modern times. Here is how someone imagined a spaceship creating crop circles:
But before UFOs and crop circles, there were fairy rings, and that is the article I visited next. They are made of mushrooms that appear (naturally) in these circular shapes, and they have been the subject of much folkloric speculation over the centuries! Shakespeare alludes to them in Midsummer Night's Dream, and here is Rackham's illustration:
To break free of the fairies' spell, you can apparently use a twig of the rowan tree, which has all kinds of folkloric and mythical powers. It can ward off evil beings, and it is called the "wayfarer's tree" because supposedly it can keep you from getting lost. In Neo-Druidry it is the Portal Tree between this world and another. Here is a rowan tree: