Yellowstone National Park
I've never had a great deal of interest in geology, and perhaps that's why, when I visited Yellowstone National Park some 40 years ago, my memories are mostly of the rustic cabin we stayed in, and the bison in the park.
Ok, so I did see lots of bison again this trip, but what astounded me is what I found under my feet: a geo-thermal wonderland! I still cannot explain what makes some of the thermal feature geysers and others boiling mud pots, but I do know there's a whole lot of bubbling and boiling going on down there.
I am amazed at the jet-engine roar of the Ledge Geyser in the Norris Geyser Basin. A few hundred yards away, a much smaller vent that hisses better than any petroleum plant I've ever driven by.
The rust and burnt orange colors at the Paint Pots, contrasting with the vivid green of the moss in the nearby hot springs stream -- stunning! Not to be out-done, the Grand Prismatic Spring presents nearly every color in the rainbow.
A landscape shrouded in the rain of the morning, with green lodge pole pines reaching into the mist, but with steam drifting up through the hills and valleys in vast puffs --wondrous.
It is scary and fascinating at the same time to think what is happening right under my feet in the Yellowstone Basin.
And a PS here for the wildlife: we spent nearly two hours one afternoon watching herds of bison munching their way across Hayden Valley, and it was almost as interesting to watch the traffic they were stopping. We also found deer, elk ,antelope, and even a wolf. Perhaps the strangest sight was a grizzly bear, appeared to be asleep, draped over the top of a bison carcass. I guess even big grizzlies feel a need to protect their dinner!