If there is a worse one in Wales than the Taff's well thermal spring then I'd like to hear it.
"Wales' only thermal spring".
It's listed on tripadvisor as a tourist attraction, but if you've ever been there it is just a damp and dirty cave, resembling and smelling like an old fashioned public toilets. Peering through the rusty gate, in the gloom you can just about make out a stagnant pool full of litter and decaying leaves. It must be about the most depressing place you could possibly imagine.
It isn't even a hot spring - the temperature is usually a pretty unpleasant 12-15 C, and I'm sure the water itself would not convey any kind of a health benefit looking at the state of it.