altena arnsberg attendorn balve bergisches land bestwig bigge brilon carboniferous coal cologne dam devonian eifel erosion forest geomorphology german language greywacke heavy industry hemer henne hesse hochsauerland iserlohn karst topography lead lenne limestone low german meggen meschede napoleonic wars netherlands north rhine-westphalia ore peneplain permian prussia quartzite reef rheinisches schiefergebirge rhine rothaargebirge ruhr sandstone sicambri siegerland silver slate sorpe tectonic uplift teutoburg forest variscan orogeny waldeck-frankenberg westerwald westphalia wikimedia commons willingen winterberg wisent world war ii zinc