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., "on the ground"). Although the modern term uses (stable, shed), this stems from the word (spot, location - cognate to the English "stead"), and is  combined with (soil, ground - cognate to the English "earth"). The German ("tunnel in mining") has the same origin. Alternative regional names are (Bavaria), and (Austria), that carry the regional names for dwarfs that folk belief has connected them to. Construction. The erdstall tunnels 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. Erdstall tunnels have only one narrow concealed entry point, with no second exit tunnel as 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: 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.