Yellowstone National Park
When I used to live in Montana, one of the favorite places to go on the weekends or a day where I didn't have classes was to drive down to Yellowstone National Park which was on the border of Montana and Wyoming. Especially on the days where there were animals laying around that you could see. Because nature photography has to be my favorite medium from flowers to mountains to lakes to animals. Which you could find mainly in the Hayden Valley.
We went to both the upper and lower basins that were covered in these hydrothermal spots and geysers. Which were very colorful but you will be smelling sulfur everywhere you go. And some areas are stronger than others.
Of course if you go to Yellowstone, you cannot miss Old Faithful which is a geyser that goes off every hour and a half. It is very short lasting between one minute to five minutes. But it does go up to 184 feet into the air and everyone stops here at least once to see it go off.
The last main place that we went inside of Yellowstone was the Mammoth Hot Springs. It's another hydrothermal location but unlike the others it's white due to the limestone. One time when we were there it was an active day while another day it was not. As some days there's barely any water discharge while other days there is more.
If I ever make it back to Montana or Wyoming one thing I would do is revisit Yellowstone National Park and probably take a few days to go on a hiking trip through some of the areas that aren't around the main road loop around the park as that was what I did each time I had visited the park before.