There are many crevices in the area. This one, a bit off the road, is so big that it forms a real cave. You can climb into the cave. Be careful: it's dripping in there!
With a short circumnavigation of the Talalpsee you have a great view of these half caves and one can easily commit! Be sure to visit when you are at Talalpsee!
The good 20m deep cave, which is written with dragon cave. From the wide entrance, which you can enter while crouching, continue standing in a semicircle to a small opening further along the path.
A 50m long tunnel in the Nagelfluhfels, the two entrances of which can be found along the edge of the forest. Over two 2m high, only the entrances are reinforced with masonry and the openings must be entered while crouching.