Beautiful lake, beautiful mountains. And here is such a ruin!
Of course, the system may not be entered. View the satellite picture via Google Maps, because there is a lot missing from the mountain "top left".
The core competence of the Swiss company group Geobrugg lies in the processing of high-strength steel wire into protective systems.
Wikipedia: Since 2001, the engineers of WSL and Geobrugg have been testing newly developed rockfall protection systems in the Lochezen test facility near Walenstadt.