Nidlenloch

Nidlenloch (also spelled Nidleloch) is a vast cave system inside the Weissenstein ridge above Oberdorf in the Swiss canton of Solothurn. With about 7.5 km of passages and a depth of roughly 400 metres, it ranks among the largest caves in Switzerland and is the deepest in the Swiss Jura. The entrance sits among meadows and forest on the ridge, close to the hiking trails that overlook Solothurn.

What kind of cave is Nidlenloch?

It is a karst cave carved into Jura limestone, mostly dry and alpine in character. There are no lights or walkways here. Visitors find a natural network of passages, shafts and squeezes that calls for a headlamp and sturdy clothes. For most walkers the cave is a stop on a Weissenstein hike, while going inside is an expedition for experienced cavers or for people in a guided group.

What is its history?

The cave first appears in print in 1828, when the geologist Franz Josef Hugi reported pushing about 350 metres inside; locals almost certainly knew it earlier. In 1868 an engineer named Moser drew a 1:1,000 plan and cross-section of the part then explored. Between 1889 and 1891 teams led by Forster and Rotschi climbed down several small shafts on rope ladders. Franz Held later led more than 60 expeditions, and by 1909 the cave counted among the deepest known anywhere. A local research group, the Arbeitsgemeinschaft Nidlenlochforschung, has worked here since 1975 and found many new passages after re-surveying the known sections.

How do you get to Nidlenloch?

The entrance is roughly five minutes on foot north of the Hinter Weissenstein restaurant. You can ride the cable car up from Oberdorf, or walk from Solothurn through the Verena Gorge and past the hermitage. A well-known day hike links Solothurn, the gorge, the Weissenstein and Oberdorf, and the cave entrance makes an easy detour from the ridge.

Can you go inside?

The entrance is locked. Experienced cavers can collect the key from the Hinter Weissenstein restaurant, for a fee and during the restaurant's opening hours. Going in alone is discouraged. Beginners should join a guided tour, which has to be arranged in advance. The Weissenstein section of the Swiss Alpine Club runs full-day cave outings, for example one on 24 October 2026 that starts at the lower cable car station. Check current prices and rules before you travel.

What else is nearby?

In Oberdorf, at the foot of the mountain, you can see dinosaur tracks about 145 million years old. The Weissenstein is also one of the Jura's main viewpoints, with Alpine panoramas in clear weather, and the Verena Gorge with its hermitage is a classic trailhead.

Frequently asked questions

How long and how deep is Nidlenloch?

Sources vary: length around 7.5 to 8 km (one gives 7,561 m) and depth between about 394 and 407 metres, depending on when and how it was surveyed.

Is Nidlenloch open to tourists?

There is no ordinary show-cave route. The entrance is locked and the key comes from the Hinter Weissenstein restaurant. Without experience, book a guided visit.

How far is the entrance from the restaurant?

About five minutes on foot to the north.

When is the best time to visit?

During the hiking season, when the cable car and restaurant are running. Guided trips into the cave are also held in autumn.