We love this place! We have been to a few different free hot springs or thermal baths but this is by far the best one. Its a natural spring in the middle of the Pyreenese mountains, near the border between France and Spain and its so beautiful.
You go off the main road up a few hairpins and park by the road. There is a trail leading from there to the hot spring and only the road there is beautiful. From a distance you can see the steam from the hot water, like a picture from a fairy tale.
A waterfall with different levels and pools, steaming hot in the cold mountain air. The water is around 60'C and the sourroundings is absolutely stunning. Montains with snowy tops and far away from the civilisation. Its hard to find this place but once you get there its worth the difficult way there.