We've driven back to the Grand Prismatic Spring parking area, crossed the bridge over the Firehole River and started up the boardwalk. You can see Sandi in just about the center of the picture, and, in the background, the steep hill we just climbed.
Unlike Sandi and I, these are tourists. Oh, well, we're tourists, too.
The spring is about 250 feet wide and 160 feet deep, and colored by thermophilic bacteria. The water is HOT!