The caves and gorges are a bit off the marked trails. Most walk along these (beautiful) paths and do not venture into the ruts that would inspire any geologist.
very interesting story, the secret tunnel, in case of emergency, if it had been necessary in case of war, to blow up the Devil's Bridge, then this would have been the connection
Only for sure-footed hikers with a head for heights. An old, poorly maintained military trail with a small cavern passage and ladder section. Up the Schöllenen Gorge directly to the old artillery observation post and the Bäzstrasse. Quite an adventure.