Zelénci is an underground source of Sava Dolinka, in the municipality of Kranjska Gora. Here, the water boils during the day from a green lake up to 2 meters deep. Because of this distinctive green color, the spring got its name. Zelenci is a nature reserve and home to many endangered animal and plant species.
The porous lake chalk, which is at the bottom, constantly lets ground water in the form of "volcanoes", which is a unique example in Slovenia. The lake water has a constant temperature of around 5-6 °C. The water from the lake passes into a river bed, which in the east spills into the kilometer long and 200 m wide, shallow Blata swamp. The Sava Dolinka riverbed originates near Podkoren, on the slopes of the Vitranc mountain.
In 1992, Zelenci was declared a nature reserve. Their importance lies in the testimony of events in the geological past. They also represent the habitat of interesting animals and the habitat of rare and endangered plants. The unspoiled nature of Zelenci with its surroundings with many springs and an emerald green lake found its place on the painting canvases of Ladislau Benesch.
Sir Humphry Davy, the famous naturalist, preacher of the beauty of this mountain landscape, wrote with all sincerity: "I liked the Sava Valley with its waterfalls and lakes the most. I don't know anything more beautiful in Europe."
The area of the nature reserve is 14 ha. Explanatory boards and a viewing bridge with a tower are placed along the well-maintained paths.