Grüner See, literally “Green Lake”, is a lake in Styria, Austria, near the town of Tragoss, located at the foot of the snow-capped Hochschwab mountains. During winter, the lake is only 1–2 meter deep and the surrounding area is used as a county park. It is a particular favourite site for hikers. But as the temperature starts rising in spring, the ice and snow on the mountaintops begins to melt and runs down into the basin of land below. The lake swells up to engulf the entire area including the park. During summer, the lake reaches its maximum depth of around 12 meter and is claimed to look the most beautiful at this time.
The lake gets its distinctive green colouring, and the name, from the grass and foliage beneath, and thanks to the fresh snow melt, the ice-cold water is crystal clear clear. The temperature of the lake is rather cold at 4 to 8 °C, yet it’s popular among divers who can observe the green meadows in the edge zone of the lake particularly in June when the water is at its highest. The alpine grasses and flowers of the meadow are visible in full bloom under the water. One can even see benches, a bridge and walking trails. Starting July, the lake starts to recede and by winter, the lake is back to its original size and the park is returned once more to the hikers.