Useful Information

Location: Near Hinterbrühl.
17 km from Vienna. From Vienna use the Südautobahn to Brun, then A21 towards Salzburg. Exit Gießhübel.
(48.086192, 16.257664)
Open: APR to OCT daily 9:30-17.
NOV to MAR Wed-Fri 9:30-14:30, Sat, Sun, Hol 9:30-15:30.
Fee: Adults EUR 18, Children (5-14) EUR 12, Seniors (60+) EUR 15, Families (2+1) EUR 42.
Groups (20+): Adults EUR 16, Children (5-14) EUR 10.
Classification: SubterraneaRock Mine SubterraneaFactory
Light: LightIncandescent Electric Light System
Dimension: Underground lake: Ar=6,200 m², T=8 °C.
Guided tours: D=45 min.
Accessibility: no
Address: Seegrotte Hinterbrühl GmbH, Grutschgasse 2, A-2371 Hinterbrühl bei Wien, Tel/Fax: +43-2236-26364. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1848 G. Plankenbichler had a well drilled and found gypsum.
1912 after a routine blast, water flooded the mine. Mine was closed.
1932 the new formed cave was discovered.
01-MAY-1944 confiscated by the Nazis, water pumped out and underground factory installed.
SEP-1944 start of the production of aircraft parts for the Nazis by forced labourers.
APR-1945 destroyed by the Red Army.
31-MAY-2004 five visitors die in boat accident.
2020 closed for renovation.


A catastrophy in a gypsum mine created Europe's biggest subterranean lake. In a routine blast in 1912, twenty million litres of water flooded the mine, so it had to be shut down.

When G. Plankenbichler had a well drilled in 1848, he found gypsum close to the surface. He decided to mine the mineral and throughout the following decades, miners dug the ground. Gypsum was used as a fertiliser.

The mine was closed in 1912, after the mine was flooded. In 1932 cave explorers discovered a fantastic natural monument which had developed in the abandoned mine. The 6,200 m² lake is the biggest underground lake in Europe. Soon workers started to build safe paths to the subterranean lake and install electric light. Finally, boat excursions into the former mine became a tourist attraction.

By the end of World War II, water was pumped out of the grotto and the cave was used as an underground factory by the Nazis. 2,000 people, many of them forced labourers, had to build parts for the Heinkel HE 162 aircraft, the first jet fighter of the world. The Red Army destroyed the factory at the end of the war. After the war it took some years to restore the mine and reopen it to the public.

On the tour you see rooms that once served the miners as a chapel, common room and wine cellar, where they used to celebrate. There are even stables for working horses which had to spend all their life in the dark. The lake - which gave the mine its name Seegrotte - is situated at a depth of 60 meters below ground. A romantic boat ride takes you into a quiet and magic world. This place is very popular, 250,000 people are visiting the Seegrotte every year.

But on Whitmonday 2004 this romantic boat ride became a death trap for four tourist from Germany and one from Belgium. The trimaran, they were sitting in, had a technical problem, one of the three hulls became leaky and the boat capsized. Most of the passengers got wet but were not harmed, but four of the tourists were trapped under the boat by the balustrade of the trimaran and drowned. The attraction was temporarily closed until 02-JUL-2004. The site is now open again, but the boat trip on the underground lake is canceled for an indefinite time. The examination of the accident is not completed until now.