Nature reserve Zelenci Springs is located in Slovenia, near to the three-country border (Slovenia, Italy and Austria). It represents the source of the river Sava Dolinka, the longest Slovenian river. Underground waters flowing from the valley of Tamar re-emerge here through the porous chalk bottom of a small lake. The porous bottom permits a constant up-welling of groundwater in tiny jets, which is an unique phenomenon in Slovenia. The spring and its surrounding protected area (total 47ha) are named after the unique brilliant green color of the lake, which was admired already by Sir Humphry Davy, the famous British scientist. During his first visit in 1819 he stayed in the village of Podkoren and wrote extensively about the spring. In his book he later described the whole Sava valley as being the most beautiful valley in Europe. The lake also provided inspiration for the beautiful canvas paintings by Ladislau Benesch.

The area that includes the lake and marshlands around it was declared a nature reserve in 1992 due to the geological and biological importance. Geologically the surrounding valley is the result of glacial erosion and contains many lake sediments, suggesting that Zelenci Springs is a remnant of the once much larger lake created by the retreat of the glacier. Biologically the natural reserve is home to various rare and endangered animal and plant species.

Zelenci Springs represent a unique opportunity for landscape and nature photography. The lake provides for perfect reflections of Mt. Visoka Ponca in its unique green-colored waters and the rare plant and animal species represent interesting subjects for nature photographers. The area is situated off the main road between the villages of Podkoren and Rateče. It can be reached by a pleasant 5 minute walk by maintained trails that feature informational signage, as well as viewing bridges and an observation tower.