Is It an Anomaly?

Sometime in the third millennium BCE, workers completed a massive stone structure on a plateau in northeastern Africa — a project so precisely executed that its four faces align to the cardinal directions with an average error of less than four arcminutes. That's better than 1/15th of a degree. To put it in perspective: a modern magnetic compass in the field is typically accurate to about 30 arcminutes. These builders beat that by nearly an order of magnitude. Here's the catch: they had no iron tools, no magnetic compasses, and no surveying instruments we've confirmed. The structure's base spans roughly 230 meters per side, and the workforce numbered in the tens of thousands. Two serious hypotheses have been proposed — one involving sightlines between two circumpolar stars at a precise moment of meridian transit, another involving nothing more exotic than a stick, a string, and knowledge of a specific calendar date. Both are technically feasible. Neither has been definitively proven. No papyrus, no tool kit, no construction diagram has ever surfaced to settle the question.