This is a photo of my wood fired stone hot tub. no liner just field stone, mortar and a sealer. I use sea and Epsom salts with a ionizer filter. As far as I know this is a one of a kind hot tub. I was inspired to build it after soaking in a natural hot spring in Steamboat Colorado
This pool is awesome. Hidden pools. The ground moves up and down. Can be the cover for a patio. And have different depths: A wadding pool for children, and paddling pool/spa depth, and big pool/ cannon ball depth. Floor/cover moves in 2 minutes.