Dear Traveller,
if you like to swim or drink healthy water, you should visit Slovakia in Europe Union 
I am proud of this nature article, and hope, that the environment feeling of this and the next generations will keep these sources clear for use.
Slovakia has almost 1600 water sources of mineral or thermal water. 23 mineral sources are officially declared as positive for health.
Thermal sources are for many decades used for SPA purposes. I had enjoyed few of them and are summarized in my favorite SPA wellness list
see you in some of them,
enjoy,
J.
* Full information in the native language (Slovak) is available here.