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.
depth: