An amazing if rather short (+80m?) intermediate level VF (C/D KS3+) INSIDE the mountain, but with rock cracks that let in just about enough light, plus an exposed section leading to a seat on the cliff face to enjoy the view. :-) Note that the start includes a short zipline to ensure that everyone that enters has the right equipment and knows what they are doing. Other interesting features include climbing up & along wooden logs at various points (avoid when wet). The route is well protected & has a picnic table and viewing area at the top. A headlamp can be useful as photography inside is difficult. The old-world "cable car" up costs 7 CHF each way. At the end cont. on to Seewlisee for great views (T=+/-1,050m).