That's what I was thinking. What are these things?
Well, they're rocks. Big massive piled up rocks. Just sitting a few miles south of Mammoth Hotsprings strewn about the hillside. Watch for that turn off the loop coming from the North or your bound to miss it.
The thing about the Hoodoos though is that they scream exploration. I mean, you can't help but climb them, and me being a climber type person that climbs anything that is climbable, I couldn't resist.
Hoodoos, strown about everywhere. You can spend as little as ten minutes or as much as two hours here, depending on your available time, they are everywhere and there is much to explore.
I could spend an entire day here. A recommended place to check out on your way through Yellowstone.