Since this area is very volcanic,
there are loads of thermal baths. Some are very remote, barely developed and consisting of a few bathtubs with water in them. Others are developed pools. Our favorite one, where we spent at least 4 hours soaking was called Termas Geometricas. They were built into a narrow river canyon which had a cold river and also hot thermal water close together. While there was a definite structure as you will see in the pictures, they were also created with an eye to blending in with the natural landscape. There are 14 pools and we tried them all, except the waterfall pool at the top which Dan tried for a microsecond.
After bathing we joined other clients in a beautiful lounge at the bottom with a common fire pit and hot coffee and cinnamon rolls.