Seegrotte Hinterbrühl, Show mine in Hinterbrühl, Austria
Seegrotte Hinterbrühl is an underground mine featuring a large lake system within its tunnels and chambers. The water fills sections that were once worked for gypsum extraction, creating a striking natural landscape beneath the surface.
Mining operations began in the middle of the 1800s when workers systematically extracted gypsum from the rock. Water infiltration forced the shutdown of production, and the site later transformed into a destination for visitors to explore.
The name comes from the underground lake that forms the heart of the site. Visitors can see the old tunnels and chambers where workers once extracted gypsum, gradually creating this natural body of water below.
Wear warm clothes because temperatures stay cool year-round beneath the surface. Tours last around 45 minutes and guide you through both dry passages and areas where water meets the tunnels.
During World War II, this site functioned as a hidden factory producing aircraft, with manufacturing taking place deep underground. Traces of this secret industrial chapter remain visible in the tunnels today.
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