Seegrotte Hinterbrühl (bányató / flooded mine)
The Seegrotte in Hinterbrühl is a former gypsum mine that flooded after a blast in 1912; today it is a show mine with boat tours on an underground lake of about 6,200 m². Most of the lake is shallow, but shafts lead deeper. Lower Austrian fire-brigade divers have trained here in about 8 °C water, including a dive down a roughly 10 m shaft, and reported that the slightest movement stirs up gypsum dust that clouds the water for days.
Facts
- Region: Austria – Styria, Lower Austria & Burgenland
- Area: Lower Austria
- Level: advanced
- Current: low
- Type: cave
- Coordinates: 48.0861251, 16.2573426 (approximate)
- Highlights: former gypsum mine flooded in 1912 – Europe's largest underground lake (about 6,200 m²), water around 8 °C, fine gypsum silt that clouds the water for days, used for fire-brigade diver training (search exercise, 10 m shaft)
- Unverified: Only a fire-brigade exercise is documented (vienna.at); we found no source on recreational diving, a ban or a permit procedure. Depth not published (average water depth about 1.2 m according to Austria-Forum).
- Tips: No public diving is offered: dives have only been documented as fire-brigade training. Contact the show-mine operator (seegrotte.at) if you are interested; overhead environment, zero visibility once silted – mine/cave certification is essential.