passageway inside a pit cave with lights on, tourist attraction in germany

access adventure adventurous alps ancient attraction cave cavern caving cliffy deep destination dolomite dolomitic dolostone eerie europe excursion explore geological geology german germany hall illuminated inside karst laichinger landscape lighted lights lime limestone mystic natural nature passage passageway pit rock rocks rocky rugged scene scenery shaft shafts staircase stairs stairway steep steps stone swabian tiefenhohle tour tourism tourist touristic underground underworld upstairs vertical visitors walkway