Switzerland · about 29 km from Weesen
Hölloch
Info · exploration
Information only: the Hölloch can only be entered with a guide from Trekking Team AG, which owns the main entrance, or as a researcher of the Arbeitsgemeinschaft Höllochforschung (AGH); there are no freely accessible entrances. All known dives were research dives on AGH expeditions (mainly 1962–1997); no arrangement for visiting divers is known.
- Max depth88 m
- CertificationFull cave
- SpecialRopework
Diving and fills
Dive here with
No dive centre guides here yet. Do you dive here with guests? Add your centre for free →
Fills nearby
- Tauchschule Divepad.ch (Urdorf)Air, O₂, helium, trimix 18/45 (premix) and argon
- Tiefenstein UnterwasserWelten (Horn, Bodensee)Air, nitrox 32, trimix 18/45, O₂ (Divox), helium and argon; 230 and 300 bar
Now at Hölloch
The dive
The Hölloch is a maze of passages on three levels, the lowest of which lies largely below the karst water table; almost two thirds of the system is flooded at times or always.
2 earlier accidents or incidents have been reported at this cave. Read what happened ↓
Profile and sections
The Hölloch is a maze of passages on three levels, the lowest of which lies largely below the karst water table; almost two thirds of the system is flooded at times or always. In the largest sump the Riesengang descends to -88 m and comes up again 823 m further on as the Osiris passage, the Fjord. After 225 m the Badewanne-Schlot sump, in a passage 6 by 3 m, still keeps going down.
The cave has been explored since the 1950s, since 1968 by the Arbeitsgemeinschaft Höllochforschung (AGH); according to the AGH it is 213 km long with a height difference of 1033 m. In 1962 and 1963 members of the Tauchclub Basel dived the Riesengang and Fjord sumps; the second dive was abandoned because the water turned murky. From 1967 to 1993 Basel divers tried the Zürichsee and the Blinddarm. In 1995 Hans Meier dived the whole Riesengang–Fjord sump, proving the two passages are one; up to 1997 he also dived the Badewanne-Schlot sump and the Zürichsee. In 2011 members of the AGH and SGH scouted the Bachschlucht sump via entrance E4 for a new dive, but carrying the gear proved so hard that a dive became doubtful.
Practical: the AGH runs no tours itself; tourist trips, as far as the underground waterfall Wasserdom, go with guides from Trekking Team AG.
- Depth and profile
- Several sumps · Riesengang–Fjord sump (Osiris): 823 m, down to -88 m (through-dive 1995) · Badewanne-Schlot sump: 225 m, -54 m (1997, still descending) · Zürichsee: 140 m, down to -30 m (1997) · Siphon-Stollen: -30 m (1981) · Jümargang sump 3: 160 m, -15 m (1984) · Teufelssiphon to the Nirwana: dived through in 10 min (1994) · Bachschlucht sump: dived before by Philippe Rouiller, aborted because of technical problems; scouted in 2011, not dived
- Configuration
- No data on configurations or gases. All gear has to be carried through dry cave for hours; earlier dives stopped at the limits of their equipment. The cave air is 6 °C.
- DPV: unknown
- No data; all gear has to go through hours of dry cave.
- Gas
- Trimix from 45 m
Who can dive where
- At least Full cave
- Configurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
- Configuration unknown — research beforehand
- Goes down to 88 m (trimix or deco may be needed)
- Ropework (SRT) needed
- Experienced divers only
This is how the planner decides who in your team may dive this cave. Rules your own trip adds (organizer, a mail, the AI) show with your trip.
How to get there
The main entrance (E1, 735 m) lies at Stalden above Muotathal, a short walk from the Hölloch Center (Stalden 14). The sumps lie deep in the lowest part of the system and can only be reached after hours of caving with ladders, ropes and lakes; the 1963 dive expedition took 38 hours in all. The Bachschlucht sump is ~3 to 3.5 hours from the high entrance E4, with ~400 m of height difference, shafts, a meander, tight squeezes and poorly or unprotected climbs; you reach the water by a ~4 m abseil, and the only place to kit up is a rock of ~1 by 1.5 m. The long trips run in winter, roughly from early November to mid-March.
Around Hölloch
Fills2 fill stations · nearest 53 km
Tauchschule Divepad.ch (Urdorf)
Urdorf (ZH), Switzerland — street address: ask
Air, O₂, helium, trimix 18/45 (premix) and argon
24/7, access via app (with a subscription)
Fill-station subscription CHF 85 a month (CHF 65 for rebreather-only divers). Without a subscription, per bar-litre: helium CHF 0.080, O₂ CHF 0.030, trimix 18/45 CHF 0.050. Whether visitors without a subscription can fill: ask (WhatsApp).
Tiefenstein UnterwasserWelten (Horn, Bodensee)
Seestrasse 19, 9326 Horn, Switzerland
Air, nitrox 32, trimix 18/45, O₂ (Divox), helium and argon; 230 and 300 bar
Tue–Fri 10:00–12:00 and 13:30–18:30, Sat 8:00–16:00; closed Mon; outside hours by appointment. 24 h outdoor stations: air and EAN32, one also trimix 18/45 (top-up card, CHF 50 deposit).
Visitors can fill on showing their certifications. Prices per 100 l: air CHF 0.50, EAN32 CHF 0.60, trimix 18/45 CHF 6. Annual flat rates CHF 150–300. In eastern Switzerland, far from Lake Thun.
Other sites1 within 34 km
News
All (2)
Accidents and incidents
What happened at this cave before, with the sources. No names are given; read it as a lesson for your own planning.
- In January 2018 eight men on a two-day tour were trapped for six days after unexpected rain filled a sump on the way out; rescuers reached them via another entrance, and they came out unhurt.
- In August 1952 four explorers were trapped for 9 to 10 days by a sudden flood; they waited in the high Riesensaal and came out by themselves when the water fell.
Access and rules change: check what applies locally right before your trip. Source: GDELT Project and the news feeds of diving magazines. Search for more news ↗ Searched automatically, last on 8 Nov 2026.
More of the latest in Switzerland: conditions, closures and news →Going to Switzerland with your team?
Marcel finds the sites that match your team's certifications.
Plan a trip