A group of mineral springs gush out in the vicinity of Plesná. As recently as 1956, hydrogeologists recorded thirteen springs here, but twenty years later there were only five. The disappearance was mainly caused by land reclamation works.
Bretislav spring
A rich spring with the local name Plesenská kyselka springs northeast of Plesná on the right bank of the Rokytník stream. On June 13, 2016, a research group from the Faculty of Science of Charles University in Prague found a radioactive spring of Radonka south of Plesná and on June 1–5, 2017, it was treated - the Břetislav spring, named after the prominent hydrogeologist RNDr. Břetislav Vylit. It is the most radioactive surface spring in the Czech Republic. The spring has a radioactivity of 13,000 Bq per liter. Of the sources captured from deep, it is surpassed only by the Jáchymov spring Agricola with a radioactivity of 20 kBq per liter.
Photo 1-3: Radioactive mineral spring Břetislav