The Herliansky Gejzír geyser is situated in the Slanské Vrchy mountain range, an area where volcanic activity has already terminated. This fact makes the geyser a world rarity. The activity of the geyser was initiated by drilling 400 meters under the surface. Especially in the 19th century, balneology was developing In Herľany and the aforementioned well was supposed to provide a sufficient amount of water with healing qualities. The result is well known – one of the most attractive tourist stops in the eastern Slovakia was created. Eruptions of this slightly thermal, mineralized geyser occur regularly every 34 to 36 hours. The eruption lasts for 25 minutes and the water spurts out up to 15 meters high. Although its activity has been declining, it is presumed to remain active for another century.