Holloch Cave

The Holloch is one of the longest cave systems in the world - the third longest in Europe, with some 211 kilometres of passage surveyed since exploration began in 1875 and a depth of over a thousand metres. In 1968 it became the first cave anywhere mapped to a hundred kilometres. It is an active hydrological system rather than a dry show cave, which governs everything about visiting: snowmelt and heavy rain flood the lower passages fast, so tours run mainly in the drier winter half of the year and are cancelled outright when the forecast turns. There is no lit walkway. Guided trips range from a short introductory route with helmets and lamps to multi-day expeditions sleeping in the cave. The chambers, gours and rimstone pools are seen by lamp, which is a genuinely different experience from a floodlit tourist cave.

What's there

• Over 200 km of mapped passage - among the longest systems in the world.
• A live flood system - passages that fill fast in melt and heavy rain.
• Lamp-lit, not floodlit - no permanent lighting anywhere.
• Trips from hours to days - including expeditions that sleep underground.

When to go

Roughly October to April, when water levels allow. Half a day for the short tour.

Things to know

Visits are guided only and must be booked; walk-ups are not possible. Tours cancel on rain forecasts. It is cold, wet and muddy, with stooping and scrambling even on the short route. Claustrophobic visitors should not go.

Nearby

Muotathal village is at the entrance; Schwyz and Lake Lucerne are north-west.

Key facts