What's this giant equilateral triangle in the desert near the city of Surprise, Arizona for?
Update 8/21/06: Neatorama reader Jim Voss wrote: The mysterious triangle near Surprise, AZ is intriguing. I discovered a twist just to the southeast of the aforementioned triangle - an exact duplicate but turned 90 degrees ccw, at this location: 33deg 43min 07.77sec N / 112deg 31min 39.51sec W This triangle is superimposed on an airstrip and may indicate, in some way, the significance of the other. Who knows?
See also the comment by stonebird for more mysterious triangles!