cave trail through the perekop rock in mullerthal, luxembourg

cave formation geology caving rock wadi terrain stalagmite canyon cliff stalactite tunnel tree trunk soil bedrock ravine adventure person trail perekop mullerthal luxembourg rural region east canton echternach spectacular geological cliffs walk forest area located sauertal berdorf waldbillig hiking trails build offer ways explore erosion edge stone crumbling control eroded root plants earth landslide stair stairway stairs walking stairways hazard moving barrier luxemburg lux grand duchy europe waldbalaquo lleg kanton mafrac14 llerthal