The Blumau-Neurißhof powder factory was built in 1890, it housed 18,000 employees at the end of the First World War where it served Austria-Hungary (https://en.wikipedia.org/wiki/Austria-Hungary#World_War_I).
The factory was closed at the end of the second world war during which it served the Reich after the annexation of Austria by it.
More informations about the places’s history: http://www.geheimprojekte.at/firma_pulverfabrik_blumau.html
Story about an explosion of the powder factory in 1922:
The many mounds of earth with tunnels that give access to the centers of these had the function of storing the powder, in case of explosion, it did not spread to the rest of the site thanks to these earth walls. To see these formations in 3D click here. (use the wheel to rotate)