Erdstall
An erdstall is a type of tunnel found across Europe. They are of unknown origin but are believed to date from the Middle Ages. A variety of purposes have been theorized, including that they were used as escape routes or hiding places, but the most prominent theory is that they served a religious or spiritual purpose.

Etymology
There are very few historic references – a document from 1449 names the area above the tunnels as  (lit., "atop the soil tunnels"). Although the modern term uses  (stable, shed), this stems from the word  (spot, location – cognate to the English "stead") and  the related  ("tunnel in mining"), and this is combined with  (soil, ground – cognate to the English "earth").

Alternative regional names are  (Bavaria),  and  (Austria), that carry the regional names for dwarfs that folk belief has connected them to.

Construction
Erdstalls are very low and narrow – they have a height of  and a maximum width of about . Additionally, they feature very tight passages connecting one tunnel to a lower tunnel called a  (slip out), which are typically extremely narrow and impassable for some, as crawling under the slip hole, and then standing up to slide the shoulders through, is necessary to crawl into the higher tunnel.

There is only one narrow concealed entry point, with no second exit tunnel as is common with an escape tunnel system. Some tunnel systems feature loop tunnels at the end of a tunnel. Most tunnel systems are no longer than .

Classification
In his 2000 publication , Herbert Wimmer created a rough classification system for varying types of erdstall:

Type A has a single long gallery with slip passages and short side slopes
Type B has multiple levels connected at multiple places by vertical slip passages. Auxiliary construction tunnels have been found that were closed after completion. At the end of each tunnel, seating niches have been cut out or the tunnel is widened with a longer seating bench.
Type C has multiple horizontal slip passages and there is a round trip tunnel at the end or in the middle that is high enough to walk through upright.
Type D has multiple chambers that are connected through tunnels. The slip passages are mostly horizontal in this type.

Archaeology
There is almost no archaeological material to be found in the tunnels, although erdstall tunnels exist in abundance in central Europe, with over 700 in Bavaria alone. This makes it highly unlikely that they were ever used as dwellings, such as a hiding place in times of war.

The archaeological evidence is so slim that even age determination is difficult. Coal from a fire pit at  has been dated between 1030 and 1210. Coal from a heading in  has been dated between the late 10th and mid-11th century. A slip passage at  has been enhanced with stones to make it narrower with the stone additions dated to between 1034 and 1268. Coal from  was dated 950 to 1050, coal from  was dated to 950 to 1160. Ceramics found in St. Agatha have been dated to the 12th century, which seems to be the latest date of usage.

Museums
Most erdstall sites are too narrow to be usable for general tourism. A bigger walkable site is the Erdstall Ratgöbluckn in Perg (Upper Austria) that is open to the public as part of the local museum of Perg. The Erdstall am Kapellenberg in Großkrut (Lower Austria) was opened in 2007 to visitors of the Erdstallmuseum Althöflein.

See also
  – Hindus believe that crawling through the tunnel will wash away all of one’s sins and thus attain freedom from rebirth.
  – souterrain structures in Cornwall of unknown usage.

References

External links

 – study group for erdstall tunnels
 – journal report on erdstall tunnels
 – "Unser Erdstall" – detailed report on the erdstall in Gaweinsteil (found in 2007)
 – more than 700 underground passages and menhirs

Tunnels
Subterranea (geography)
Open problems