On July 17, 1991, a significant crop circle formation appeared near Barbury Castle, a prehistoric hill fort in Wiltshire, England This formation, often called "The Bicycle" or the "Barbury Castle Tetrahedron", was notable for its complex geometric design and its timing, coinciding with reports of unusual aerial phenomena and a town-wide power outage in Wroughton. The formation covered approximately 12,000 square yards and has been interpreted as having alchemical and philosophical significance, relating to the creation of the universe according to some researchers.