During a routine patrol on August 10, 1990, Idaho Air National Guard pilot Lieutenant Colonel Bill Miller spotted a strange sight from the cockpit of his RF-4C Phantom fighter jet: a quarter-mile (0.4 kilometer) wide series of intricate geometric designs, carved into the dry lake bed of Mickey Basin, located southeast of the Steens Mountains in Idaho’s Alvord Desert. The design was later identified as a Sri Yantra Mandala, an ancient Hindu symbol. But how did this large and mysterious earthwork, not there the day before, appear seemingly overnight?

Government officials declined to reveal the existence of the mandala for a month, concerned about the apparent similarities between the mysterious glyph and the crop circle phenomenon in the UK, that had suspected links to UFOs. The markings, now identified as a Sri Yantra Mandala, consisted of 13.3 miles (21.4 kilometers) of perfectly inscribed troughs, 10 inches wide and 3 inches (25.4 x 7.6 centimeters) deep, carved into the dry lake bed’s hard surface.

The mandala’s lines were laid out with machine-like precision, aligned the Earth’s true north, with the displaced soil deposited evenly along the sides of the furrow. Attesting to the precision of the mandala’s layout, the central circle is described as being "9 foot, 3 inches, with a one-inch deviation, which I consider to be a pretty doggone good circle," by Sergeant. Charlie Swindell, the officer in charge of photo quality assurance for Boise’s 190th Tactical Reconnaissance Squadron.

A search for clues as to how the enigmatic symbol was made was conducted by UFO researchers Don Newman and Alan Decker, but aside from one motorcycle track that ran through the design — apparently made by someone who failed to notice what they were driving through — no vehicle tracks were visible, and no footprints or tool markings were found at the site. Local architects had estimated that an initial land survey to plan the layout for such an earthwork would cost between $75,000 and $100,000 — this is a design that is difficult to properly reproduce on paper without drafting tools, let alone to have it inscribed with precision at a scale that can only be viewed properly from a few thousand feet above the desert floor.

Added to this is the apparent rapidness of the mandala’s appearance, as it had not been seen by the previous day’s air patrols, and Miller reportedly didn’t spot it on an earlier pass he made over the area 30 minutes beforehand — the formation may very well have taken less than a half-hour to appear

The Sri Yantra Mandala, used in the Shri Vidya school of Hindu tantra, consists of nine interlocking triangles that represent both the cosmos and the human body, surrounding a central point known as a bindu. Aside from being the symbol of Hindu tantra, the Sri Yantra also represents the union of the Devine Masculine and Feminine, with four upward-pointing isosceles triangles representing the goddess’s masculine embodiment of Shiva, and five downward-pointing triangles symbolizing the female embodiment Shakti.

About five weeks after the formation first appeared, a group of people came forward to announce that they had created the mandala with an "old-fashioned garden cultivator", pulled by three of the group’s members, and steered by a fourth, using ropes and binoculars to ensure that the symbol’s layout was perfect. Researchers began to suspect that their claim itself was a hoax, as the group claimed to have taken 10 days to create the design, a timeline inconsistent with the near-instantaneous appearance reported by the Idaho Air National Guard pilots.

The hoaxers’ story finally fell apart when they were asked to reproduce their work and failed to do so: they only managed to dig a 1/2-inch (1.3-centimeter) furrow into the lake bed, and even then they did so only with a great deal of effort. The resulting lines were also uneven, and the soil displaced by the plow was piled unevenly at the sides of the furrows, unlike what was found with the actual mandala. A professor emeritus with Oregon State University, Dr. James Deardorff, accused the government of contracting the members of the group to provide a cover story for how the mandala was formed.

In the twenty-eight years since it was first found, the enigmatic formation has since disappeared, swept away by the desert winds and the rains that occasionally flood the lake bed. But the mystery of whom — or what — created Idaho’s Sri Yantra Mandala remains.