I have a keen interest in ancient civilizations and in my childhood grew up in the south-west of England, where we visited many pre-historic hill forts such as pilsdon pen and maiden castle. Crop circles are widely seen in the area near stone circles such as stonehenge and avebury. In particular the most puzzling is an artificial mound bulit 4,500 years ago called Silbury Hill, which is near Avebury.
It's a vast construct, with its base covering five acres alone. Many people first thought it was a burial mound or even contained treasure. Who built these mounds is a mystery and what purpose they had is equally puzzling. Like in America many mounds existed before the arrival of columbus and were built by indians for tombs and great temples. Such as the effigy mounds in ohio which depicted pictures of birds and animals, the reason still unknown. Mysteries of the ancient world may never be solved, but we do know our ancestors existed then, so the anwsers are somewhere inside us all.