Sri Yantra as 13 mile long crop circle (or, better to say, geoglyph) in the bottom of a dried-out lake, which allegedly appeared over a very short period of time in 1990. It is not visible today, which fuels conspiracy theories about the aliens imprinting it in the sand and the military destroying it. Including a youtube video along with the usual info.
Name: Sri Yantra Geoglyph in Oregon
Lat, Long: 42.738105,-118.314011
Location: Princeton, Oregon, USA