Where? The senses are such uncertain things, and now mine were strained beyond their limits. The rock on which I stood… If I attempted to fix my gaze upon it, it took on the aspect of a pavement on a hot afternoon. It seemed to shift and waver, though my footing was undisturbed. And it was undecided as to the portion of the spectrum it might call home. It pulsated and flashed like the skin of an iguana.
Roger Zelazny "The Hand of Oberon"
White Pocket
Vermillion Cliffs National Monument, Arizona