Be sure to double/triple check before going.

More than one of these listed was clearly on private property but the listing had no mention.

Quinn hot springs [1] in Montana being one. It is listed as "roadside" with "camping nearby" but in reality it is a paid resort on private property.

[1]https://glaciermt.com/listing/quinns-hot-springs-resort

Super cool

ok, now do the rest of the world, and add layers for cold springs, artesian sources, mineral waters, salt, other, and drop it on OSM best one I ever saw(was in) was somewhere in oregon, inland , vast vocanic pumice plains with pine trees, and an intensly cold spiring comming up in a head pond strong enough to create a big dome of water you can swim into and freeze your ass of, and then get out in a hot desert. our planet has a bunch of awsome and decidedly odd features, which luckily have not ALL been exploited , comodified, and privatized.