This photo was downloaded from Wikipedia.
The Gardiner River is very, very cold, starting up at an elevation of 10,000 feet on Joseph Peak. Both the Indian and Obsidian creeks, among others, empty into it, and it is apparently a good trout stream. It ultimately joins the Yellowstone River to the north. Where the Boiling River empties into it people are allowed to bathe and swim. It's an amazing experience--one moment you're in hot tub water, the next in the cold flow of the Gardiner, then back to the hot tub. The current of the Gardiner is quite strong and you have to brace yourself against the rocks on the river bottom to avoid being swept away. The half mile walk to the pools keeps a lot of people away, but still there were probably 40 or 50 folks there.
By the time we walked back to the changing rooms and got to the car we were hot and sticky again. It was early evening by then and time to start making the drive back to West Yellowstone. On the way we planned to stop to see the Terraces.
Oh my God.
Travertine, bathed in warm water, can support many different kinds of bacteria and algae, which give the terraces their color.
Here again was a place I could have spent days exploring. We stayed for about an hour. I can't possibly say more than these photos can, so I'll be quiet and just let you soak it in.