Vienna Woods: Seegrotte, blue lake

Seegrotte Tour Review: Europe’s Largest Underground Lake

Seegrotte Tour Review: former gypsum mineSeegrotte Tour Review. Originally, the Seegrotte caves just South of Vienna were a gypsum mine that operated from the 1840s until 1912. The mine’s caverns, with their impressive stalactites and stalagmites, provide a glimpse into the history of mining in the region. Gliding across the quiet underground lake a boat tour takes you through a subterranean world of beautifully illuminated rock formations. 

Moreover, if you are a history buff with a hang for World War II and aircraft, the mine has a couple of surprises in store. I have toured the underground lake and former mine Seegrotte in Hinterbrühl with my family. Here is what you can expect.

From Mine To Lake

Seegrotte Tour Review: access tunnelSeegrotte Tour Review. A few kilometres south of Vienna, the Vienna Woods host Europe’s largest underground lake. In a quiet street of villa paradise Hinterbruehl an old gypsum mine opened the way to an underworld of gigantic measurements.

We took more than five minutes to cross the 400 meter tunnel, along the old mining railway track. In the mid 19th century hundreds of miners had hacked out two levels and countless halls for decades. 

Seegrotte Tour Review: underground lake reflectionsAbout 105 years ago a blasting operation hit a natural water reservoir: 20 million litres of water gushed out and flooded the mine, creating Europe’s largest underground lake. That was the end of the mine and the birth of Seegrotte. The 6,200 square metre (66,240 square feet) lake formed on the lower level. Just the little blue lake (feature photo) stayed on the upper level.

From Lake To Aircraft Hub

Seegrotte Tour Review: World War II aircraft objectsSeegrotte Tour Review. In the early 1930ies Seegrotte opened as a show mine. However, during World War II, the extensive tunnels housed  one of the largest covert aircraft production facilities of the German Wehrmacht. In 1943, during the Second World War, a forced labor factory was built on the upper levels of the cave system as a branch of the Mauthausen concentration camp.

They seized the mine, pumped out the entire 20 million litres of water and established an underground aircraft factory. During the war prisoners built dozens of Heinkel HE162 fuselages there. The operation’s code name: Languste (crayfish). At Seegrotte you can still see an original rusty fuselage, a few Wehrmacht helmets and tools, and this model Heinkel plane. The aircrafts were fully assembled close to Vienna international airport Schwechat.

After the war the water filled up again. Every day, the Seegrotte operators had to pump out water in order to keep the level to a safe 1.20 metres.

Crossing Europe’s Largest Underground Lake

Seegrotte Tour Review: ship of The Three MusquetiersOur 16 people strong group descended to the lake shore. Various vaults opened a water labyrinth. We entered a modern tourist boat together with the tour guide.

My son had secretly hoped to board the pirate ship just opposite. It was used during the filming of the Three Musquetiers in 1993.

Seegrotte Tour Review: underground lakeThe water was crystal clear as we glided from vault to vault. At the walls you could still see the lines of the former water level, quite a bit higher. In one of the vaults an illuminated fountain appeared – how kitschy – but I needed to take that photograph (see below). We filled the 15 minutes boat tour with staring and listening to more stories about the lake.

Seegrotte Tour Review: How To Get There

Seegrotte Tour Review: fountain at underground lakeSeegrotte Tour Review. Most people arrive by private car or tour bus, as there is no public transport option. From Vienna’s city centre this is a 23 kilometre drive. 

Address: Grutschgasse 2a; 2371 Hinterbrühl;

Make sure you also see the Vienna Woods’ other attractions once you venture out. Seegrotte has a constant 9 to 12 degrees Celsius (48 to 54 degrees Fahrenheit) throughout the year (we visited in December, it felt so warm!).

There is a half day guided tour from Vienna that gets you to see Mayerling, Heiligenkreuz Abbey and Seegrotte in one go.


go to Car Rental Vienna – How To Rent A Car In Vienna
go to Vienna Woods – Tour and Hiking Tips With Map
go to Burgenland – Wine, Esterhazy Palace and Neusiedlersee
go to Wachau Valley – My Favourite Trips and Danube Boat Rides

back to Day Trips From Vienna
go to Vienna With Kids
go to Vienna History
back to Vienna Unwrapped homepage


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