Looking down at the boardwalk at Grand Prismatic, in the Midway Geyser Basin. We waited almost an hour for the steam to blow sufficiently off the scene below us, so that we could photograph what we had come to see. (Cooler weather creates the wondeful steam that helps define a geyser - but if it's too cool, the geyser can remain hidden behind the vapors - too warm, and there is no steam.)