Gruner See, a vanishing green lake during snowmelt season

Located at the foot of the snow-capped Hochschwab Mountains, Grüner See is one of the most breathtaking natural wonders in Styria (Steiermark), Austria. This vanishing green lake is famous for its seasonal transformations, offering a surreal underwater landscape unlike any other on Earth. During spring, as the snow melts, the lake basin fills with ice-cold, emerald-green water, submerging meadows, trees, park benches, and walking paths, creating an enchanting underwater paradise.

Location of Grüner See in Styria, Austria

This seasonal lake with its crystal-clear waters is located in the small village of Tragöß. A village that is part of the municipality of Tragöß Sankt Katharein, in the federal state of Styria (Steiermark in German), Oberort district, Austria. Gruner See, or Gruner Lake, lies at the southern foot of the Hochschwab Mountains, a 400-km-long mountain range that is part of the Alps.

Gruner See is a seasonal green lake

The Stunning Natural Beauty of Gruner See Austria

Gruner See, situated at an elevation of 776 meters above sea level, is a stunning natural tourist destination in Austria. Surrounded by a range of three towering mountains exceeding 1,500 meters in height—Pribitz, Trenchtling, and Meßnerin—this karst lake is an integral part of the enchanting Hochschwab Mountains. The natural beauty around Gruner See is further enhanced by lush pine forests, alpine meadows, and beautiful wildflowers. 

Underwater garden of Gruner See in Austria

Why Grüner See Has Crystal-Clear Emerald Water

Gruner See receives no inflow from any rivers. The lake’s water comes solely from melting mountain snow, which is why it is so clean and clear, however, the water temperature is extremely cold, ranging from about 6–8°C. The name Gruner See, meaning “Green Lake,” derives from the emerald-like color of its water. The exact size of this vanishing lake cannot be determined, as its dimensions constantly fluctuate with the seasons. Gruner See can be considered a seasonal lake. It is truly unique because it transforms into a large, beautiful lake at certain times—specifically when it receives an abundant water supply—yet at other times, this stunning green lake simply vanishes.

The Transformation of Gruner See from a Small Pond to a Lake

From late fall through winter, Gruner See is merely a natural pond with clear water, only about 1–2 meters deep. In fact, sometimes it disappears entirely. During winter, the air temperature in the mountains drops drastically below freezing. Precipitation falls as snow and freezes on the mountain peaks, completely halting the flow of water to the lowlands.

As spring arrives (around May through June), air temperatures begin to warm. Snow and ice on the karst mountain peaks begin to melt in massive volumes. The crystal-clear meltwater flows downhill and seeps into the limestone (karst) rock, filling the lake basin to capacity. The limestone dust contained in the meltwater gives the lake’s water a distinct blue-green hue. The lake’s water level depends on the amount of snow that accumulated during the previous winter. During the summer, the depth of this emerald-green lake can reach 8.5 to 11 meters. At this stage, the entire park area—including benches, bridges, and walking paths—is completely submerged beneath the emerald-green water.

Grüner See: A Karst Lake That Can Disappear

Grüner See is a karst lake and a perfect example of hydrological phenomena in limestone regions. The intermittent lake formed in a vast depression created by the erosion of limestone by rainwater over thousands of years (a doline). The porous limestone beneath the lake contains numerous cavities, cracks, and underground channels. These characteristics allow water to seep away into the ground like a sponge when the water supply stops.

By mid- to late summer (starting in July), the supply of snowmelt from the mountains runs out. Without a new water supply, the lake’s water slowly seeps out through the pores and cracks in the karst rock into the underground river system. Combined with evaporation during the summer, the water volume continues to decrease steadily until the lake dries up, transforming into a green meadow. 

Underwater park at Grüner See with submerged benches and trees

The Magical Underwater Garden of Grüner See

While the snow hasn’t completely melted yet, Gruner See looks like a small natural pond, surrounded by a beautiful natural park with lush green trees. There are also benches in the area where you can rest. It’s truly a beautiful and romantic park! As the temperature rises and more snow melts, the lake gradually expands in size. The surrounding park, walking paths, small bridges, and benches will vanish, submerged into the lake.

The emerald-green waters of Gruner See will create a breathtakingly beautiful scene. And even more extraordinary is the view at the bottom of the lake. The submerged park will transform into a stunning underwater garden. Anyone who swims in Gruner See is sure to be enchanted by the extraordinary beauty of this underwater paradise, where there is green grass, tree trunks, and even wooden benches, walking paths, and a small bridge. This lake is also home to a variety of aquatic fauna, such as small crabs, snails, water fleas, and various species of trout. However, because the lake’s bottom consists of rock, Gruner See has very little aquatic flora.

Why Water Sports Are Banned at Grüner See Austria

Since January 1, 2019, local tourism authorities have banned all water sports activities on Gruner See, including swimming, diving, and boating. This decision was made to prevent damage to the environment of this vanishing lake. There are concerns that water sports on this disappearing lake could stir up sediment at the bottom, potentially damaging its iconic emerald green color. Of course, with this ban in place, tourists can no longer dive and enjoy the enchanting underwater garden of Gruner See.

As the seasons change and the water slowly recedes, the magic of this vanishing green lake fades, revealing the lush green meadow that was once hidden beneath its surface. It is this natural cycle that makes Gruner See so special, with its ever-changing landscape, marked by its shimmering green water and fleeting beauty. Though brief, the transformation of this emerald-green lake is a unique attraction that captivates tourists from all over the world.

(Latest update in 2026)
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