Yellowstone is a giant volcano, 40 miles around. There is one part of Yellowstone where you can almost see all the way around the "rim" of the volcano, and can kind of get the impression of what kind of BULL SHIT it would be if this little lady exploded. Which...(in case you were unaware) is 250 years overdue for eruption.
If you can somehow move past this fact Yellowstone is the prettiest place ever.