South-west England is the world capital of crop circles. They are particularly concentrated in the county of Wiltshire, where a treasure trove of ancient history includes the Neolithic sites of Stonehenge and Avebury both crop circle hotspots. Reports of mysterious patterns appearing in wheat, barley and corn fields in the area began to circulate in the 1970s, but it was in the late '80s that the phenomenon exploded. Circles began to appear more frequently and became far more ornate: some resembled trippy fractals; others rune-like hieroglyphs; others stylised animals recalling those of the Nazca Lines in Peru. The intricacy and size of the formations, coupled with the fact that they would appear overnight, seemingly out of nowhere, baffled locals and farmers alike. In 1996, a crop circle appeared opposite Stonehenge depicting a mathematical fractal called a Julia set; a similar formation that emerged on Milk Hill in 2001 was one of the largest ever, stretching 900ft. A 2008 formation near the Iron Age hill fort of Barbury Castle required decoding by an astrophysicist, who concluded that it was a geometric representation of the first 10 digits of pi. The phenomenon peaked in the 1990s and early 2000s, but continues today; an average of 30 crop circles appear each year in the UK, around 80% of them in Wiltshire. Formations reported in 2021 have included a hexagonal pattern overlaid with spirals in Avebury, and a pattern of concentric "bubbles" in Tidworth Down.