@jimmy @Meyerweb The landscape in the Rhine valley is extremely flat, open fields after open fields.
But suddenly you see a lonely hill, kilometers long, it's almost reassuring to see something standing out.
But the hill is weird, it's almost geometric, and it's sides lack any sort of erosion channel, the top is extremely regular.
Suddenly I understood : that huge hill standing out in the plain is next to the mine. It's the rejected soil that stood above the coil, rejected and piled on the side.