The History of the Seegrotte Mine
South of Vienna, there is a mountainous area called Hinterbrühl. In this area, in the heart of one of the mountains, lies the Seegrotte, where a mine for various gemstones operated for many years. In 1912, after a controlled explosion in the mine for expansion purposes, a huge underground water reservoir was discovered. About 20 million liters of water flowed forcefully into the lower level of the mine, flooding it completely.
After the great flood, the mine ceased regular operations and for many years served as a tourist attraction, even before World War II.
During World War II, the Nazis were looking for a safe and protected place to produce airplanes for the war effort. Since this mountain area was safe enough from aerial bombardments, the Nazis established a small labor camp there and used the old mine in the mountain. The Nazis’ underground factory was built mostly of concrete and included a complex system of passages and large workrooms, above the flooded area.
About 2,000 people worked in the factory, producing the fighter planes used by the Nazi army during the war.
After the war, the site returned to being a popular tourist destination.
The Underground Lake
As mentioned, the mine has two levels, with the lower one lying 60 meters underground. This lower level eventually flooded and now contains a large lake, up to 1.2 meters deep. The water is cold and clear, but don’t expect to see any wildlife—it’s an artificial lake.
Since the groundwater in the area continues to flow into the mine at all times, large pumps are used to pump out about 50,000 liters of water every evening to maintain the water level and prevent it from rising too high.
Guided Tour in the Old Mine
Today, you can visit the mine and the lake as part of a guided tour that lasts about 30 minutes. During the tour, you walk deep into the mine, through the tunnels and workrooms of the Nazi factory. Along the tunnels, old work tools and remnants of airplanes left in the factory after the war are displayed.
At the end of the tour, you descend to the lower level and take a short boat trip on the large lake with an electric boat.
This is what the tour in the mine looks like
Additional Essential Information for Your Visit
Please note: The air in the mine is humid, and the walking paths are partially wet. It is important to wear closed-toe walking shoes. Additionally, the temperature deep inside the mine is lower than outside (9°C all year round), so it’s a good idea to bring a jacket, even if it’s hot outside.
Operating Times:
- From April 1st to October 31st: Every day (Monday to Sunday) from 9:00 AM to 4:30 PM. The last tour is at 4:30 PM.
- From November 1st to March 31st:
- Mondays – Closed
- Tuesday to Friday from 9:30 AM to 3:00 PM. The last tour is at 3:00 PM.
- Saturdays, Sundays, and holidays from 9:30 AM to 4:00 PM. The last tour is at 4:00 PM.
The attraction is open all year round, regardless of weather conditions. Tours depart every 30 minutes – regardless of the number of participants.
Entrance Cost to the Underground Lake (including boat trip):
- Adult: €18
- Child (5-14): €12
- Family ticket (2 parents + 1 child): €42
- Senior (over 60): €15
- Child under 5: Free
Official Website
How to get to the Underground Lake from Vienna?
From Vienna’s main train station, Wien HBF, take a regional train (platform 1-2) that goes to the village of Mödling on the outskirts of the city. Get off at the Mödling Bahnhof station. From the bus platform outside the station, take bus line 264 or 265. Get off at the Hinterbrühl Helmstreitgasse stop and from there walk about 5 minutes to the underground lake. The total journey time is about 50 minutes.
Another option is to travel to the last underground station on the U6 line, called Siebenhirten, and from there take bus line 260 and get off at the Hinterbrühl Gießhübler Straße stop. From there, it’s about a 5-minute walk to the underground lake.
Check the train schedule and purchase tickets
Address: Grutschgasse 2a, A-2371 Hinterbrühl
Map:
Other Attractions in the Area
A short distance from the underground lake is an ancient castle belonging to the famous noble family, the Liechtenstein family. You can take a tour of the castle and be impressed by this ancient structure. From the underground lake, you can walk about 20 minutes to the castle or take bus line 260 for one stop and get off at the Hinterbrühl Mannlichergasse stop. From there, it’s about a 12-minute walk to the castle. Read more information about Liechtenstein Castle.
