The biggest underground lake in Europe – the Seegrotte

Ogi Savic | Live the World

November 23, 2022

Austria is a very interesting country with a lot of tourist attractions. This time, I will represent you the biggest underground lake in Europe named the Seegrotte. It is located in a small village Hinterbrühl in the Austrian province Lower Austria, very close to Vienna. This lake is a combination of a natural occurrence and a human factor. Because it is formed in the former gypsum mine, it is man-made. However, being fed by seven springs, it is also a natural occurrence. The lake's surface is huge. It has 6200 square meters. Since the lake doesn't have any natural drainage, and in order to keep the level of water low and the cave accessible to the tourists, every day 50 to 60 cubic meter have to be pumped out into a nearby creek. The depth is kept to around 1,2 m.


From a mine over the Nazi factory to a tourist attraction

The gypsum deposits were being mined here since the 18th century. However, in 1912, a blast caused more than 20,000 cubic meters of water to flood the mine making it unusable. For years, the mine stood still, until the Viennese entrepreneur bought it. First, he wanted to establish an amusement park, afterwards a champignons breeding, but it didn’t work because the temperature was too low. In years that followed, a 200 meters long tunnel was dug in order to access the mine. Since 1932, the underwater lake was opened to the visitors, and an electric boat was introduced.

During the World War II, the** **Germans used this mine first as a storage, and since 1944, an aircraft factory was set up in the tunnels, since they were relatively safe from the bombing raids. For the aircraft production, the lake was pumped out, and a concrete bottom surface was made. The hulls of the Heinkel He 162, also known as the salamanders, were built as the prototypes here. They were later transported in parts and assembled at the site of today’s Vienna Airport in Schwechat. Around 600 Mauthausen concentration camp prisoners had to work under the inhumane conditions in the tunnels.

Photo © Credits to Bundesarchiv, Photo 141-2737


After the World War II, the mine was filled with the water again, and since then, it is one of the tourist attractions in Lower Austria. The Seegrotte is located just 12 km from Vienna and it offers 45 minutes long guided tours with a ride on an electric boat over the lake. There are two lakes - a small one called Blue Lake and a Big Lake, that is located 65 m under the surface. The mine can be visited all year round, and the air temperature is always 9°C. The parts of the mine served in 1993 as a film set for Walt Disney's film "The Three Musketeers". You can still see the scenery and a dragon boat from the movie. Around one quarter million tourists visit the Seegrotte, the biggest underground lake in Europe, every year, so you should do that it as well.  

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