mullerthal trail in luxembourg, perekop canyon, hiking through a forest with sandstone rock formations

aesbech ardennes autumn basalt berdorf canyon cave den echternach erosion europe forest formation formationn formations geology gorges green hiking hohllay hole huel landscape lee loup luxembourg luxembourgish moss mountain mullerthal natural nature outdoors path perekop rock rocks sandstone stone summer swiss switzerland toursim trail travel tree trees valley wall wolfschlucht wood woodland