Much of the world is filled with tunnels. The aqueducts of Rome were largely dug to be underground, and the catacombs were massive systems of tunnels where people buried their dead. However, these tunnels all have a known purpose. There are many tunnels in Europe which are known as Erdstall, and these are a true mystery.

These Erdstall tunnels, most likely built in the Middle Ages, are characterized by being very low and narrow, usually ovular in shape. Their lengths tend to extend from anywhere between 20 and 50 meters. One other thing featured in the Erdstall are the Schlupf, which means “slip out.” These are incredibly tiny holes which are used to connect different tunnels at different elevations. The Erdstall exist mostly in Bavaria, an area in Germany, but, mysteriously, tunnels have been found in Austria and even as far as Britain and France. However, while the tunnels themselves seem unimportant and not special, their function has baffled historians for years.

There are many theories which have been suggested. One states that perhaps they were escape routes, however, with only one entrance and exit point, the Erdstall would not be very effective at this. Another theory has said that maybe the Erdstall were used as hideouts, however being so narrow and with virtually no air flow and having only one entrance, they would not be very suitable for this purpose either. Perhaps the Erdstall were used as storage. Even this could be debunked by the narrowness of the tunnels, being that these are not very effective for storage. Many Erdstalls also exist below the water line, meaning that many of them can become flooded at times with water, again not very effective for storage purposes. The most substantiated theory states that these tunnels were used for some religious purpose. However, religions are usually very well documented, and no records exist which explain the Erdstall. Thus, the tunnels remain a mystery and most likely will for a long time to come.

These Erdstall are a shining example of unsolved mystery. As much as everyone would like to find out their purpose, it is unlikely that this mystery will ever truly be solved.