Yeah it is a hot spring. only about 100 feet off the road. They are all over Idaho. This was near warm lake.
If you look close, there is a white drain pipe on the left side that has a pllg on it, you use it to drain about three or four inches of water out, and there is a vale on the right side that lets cold water in to regulate the tempature. The water comming off the rocks is the hot water, and buy itself is too hot to sit in.
This particular pool is one of the main reasons I went back to Idaho. The water is mineral rich, and seemed to work wonders for my skin. I had been in vegas for almost two years, and my skin was really dried out.
If anybody ever travels to this part of the country, I could give real easy directions.