Slovakia
A small open-air mineral pool in the village of Liptovský Ján, fed by a natural spring. The water is lukewarm rather than hot, locals treat it as a cold-ish plunge and swear by it, and it's free, sitting right in the village with shops and pensions nearby. A quick dip rather than a long soak, best combined with hiking in the Low Tatras above.


Kończysty Wierch Mountain
Proposed
Kalameny hot spring
Verified