Erdstall Tunnels: Europe’s Narrow 'Wormholes' and the Mystery Within

Walking the edges of her Bavarian farm, Beate Greithanner discovered one of her cows suddenly sink into the ground — the animal had fallen through the hidden entrance to a network of extremely narrow underground passages known as erdstalls. These puzzling tunnels, with distinctive features and constrained dimensions, have baffled researchers for more than a century.

What are erdstalls? The German term roughly means "earth stable" or "earth place." Folk names — mandrake caves, goblin holes or dwarven burrows — reflect local mystique. Physically, many erdstalls are roughly 1 metre tall and about 60 cm wide, with poor air circulation and typically a single entrance and exit. Small vertical or horizontal openings called schlupfs (slip passages) — about 30–40 cm wide and 40–50 cm tall — link levels within some systems, which can extend up to ~50 metres. Explorers also report bench-like ledges and stair-like cuts carved into the passage walls.

Classification and distribution

Researchers group erdstalls into four broad types: Type A — long, mostly horizontal passages with a few slipouts and gentle slopes; Type B — more complex, multilayered systems with vertical slips, niches and possible seating areas; Type C — relatively roomier passages with horizontal slipouts; and Type D — larger interconnected chambers. Around 2,000 erdstalls are recorded across central Europe, including roughly 700 in Bavaria and 500 in Austria, often situated near historic settlements, churches, cemeteries or gently sloping woodlands.

History of study

The systematic modern study began in the late 19th century when Benedictine priest Lambert Karner explored and catalogued hundreds of tunnels in Lower Austria. He described them vividly:

"strange winding passages where one can often only force oneself like a worm."

Karner compiled his observations in a monograph published in 1903 that remains influential in German-language scholarship.

Dating and finds

Investigations have produced mixed evidence. Radiocarbon dating of timber from one erdstall has returned dates between about 950 and 1100 CE, and occasional charcoal or pottery sherds of medieval vintage have been found. Yet many passages appear deliberately cleared of domestic debris — described by some investigators as "swept clean." That uneven archaeological record makes definitive dating and function hard to establish.

Theories and debate

Scholars have proposed several explanations, none universally accepted:

• Temporary refuge/escape routes: Some researchers argue erdstalls were short-term hiding places during raids in the 11th–13th centuries. Josef Weichenberger, a proponent of this view, experimented with staying in an erdstall and reported breathing difficulties in confined sections but improvement in larger chambers.
• Food or ice storage: The stable, cool conditions underground could have been useful for preserving food or ice, though archaeologists have not found clear remnants to confirm this use.
• Older origins: Others, including Dr Heinrich Kusch, suggest many examples may predate the medieval period — perhaps reaching back to the Neolithic — noting similar narrow subterranean systems across Europe.
• Ritual or funerary use: Some anthropologists propose ritual, funerary, or symbolic functions, interpreting niches and seating as part of ceremonial practices.
• Folklore and popular speculation: Local legends credit supernatural beings (goblins or dwarves), while online theories sometimes compare erdstalls to paleo-burrows created by megafauna; specialists reject the latter because paleo-burrows are typically much larger and contain distinct faunal traces.

Critics of the refuge hypothesis note practical problems: cramped dimensions, limited ventilation and a single entrance make sheltering groups risky — a fire or flood could be fatal. These physical constraints weigh heavily in the debate over function.

Safety and modern interactions

Because of low ceilings, constricted passages and seasonal flooding, most erdstalls are closed to the public. Inexperienced explorers risk becoming trapped, suffering hypoxia or drowning during high water. Nonetheless, a few landowners run supervised experiences: for example, an innkeeper in northern Austria offers a guided crawl into an erdstall on his property for adventurous visitors.

Conclusion. Erdstralls remain enigmatic. Sparse finds, regional variation, and their unusual architecture mean multiple functions are possible across time and place — temporary refuge, storage, ritual use or much older origins. Until more systematic, multidisciplinary investigations are carried out, the tunnels will continue to attract archaeologists, spelunkers and folklore enthusiasts alike.