Download DEM for balckforest and upload to geoserver

[JesJehle]

[JesJehle]

Have a look at this article: https://betterprogramming.pub/using-3d-terrain-in-your-web-apps-1c0c56ae07e1
It seems, they have provided a free terrain model.
@mmaelicke you should implement this. Have a look