South East of Krabi town, are popular hydrothermal pools. Here you can bathe in the naturally hot spring water, stuffed full of invigorating minerals. Well that's the claim, I went at Songkran, and the pools were packed with Thai people on holiday. It's better to visit at a less busy time, I think.
There's a nature area and places to eat, and toilets to change in, but you're ultimately sitting in green mineral hot water, I think it's better to visit a spa.
There are two sites here, not far from each other. A hot spring site with pools of hot mineral water and about 6km further away, a natural area with many ponds, blue pond, emerald pond and volcanic ponds, most of which you cannot swim in. Only the emerald pond was open for swimming. The blue pond is nice to look at, and a bit of hand clapping causes bubbles to rush up from the bottom, but I prefer more interactive fun and the blue pool is a mere photo opportunity.
For the pond area, I preferred to find one of the streams, downstream from the temple on the site, and relax in that. That way, you're away from the crowds and it's much more relaxing laying down in a fast moving volcanic stream.
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