Probably the most famous of Chacoan astronomical markers is the so-called Sun Dagger, found high on a shoulder of Fajada Butte on the southeastern floor of the canyon. Three vertical slabs of sandstone lean against a cliff. They are aligned in such a way that a thin "dagger" of sunlight shines through the slabs and onto the cliff face at noon each day. there, people carved two spirals into the rock. At approximately noon on the summer solstice, the light falls on the middle of the larger spiral. At winter solstice, two shafts of light bracket the outer edges of that spiral. At spring and autumn equinoxes, a smaller shaft of light bisects the smaller spiral.
