An Erdstall is a man-made cave built under a dwelling house about 800 years ago. It has features such as various chambers, loopholes and seating niches.

Every drive destroys these structures, which are hewn in clay or granite granules. This cultural asset must be protected. At the same time, the Erdstall Centre would like to present this topic to the public, both digitally and analogously. There is a museum in Unterstetten (Grieskirchen district/Upper Austria); lectures and guided tours take place there.

There are about 30 drive-in Erdställe each in Upper Austria, Lower Austria and Bavaria. The purpose of these buildings is not clearly defined: refuge in case of robbery, pantry, or cultic site are all possible explanations. Comparative research of settlement movements, documents, and dating can distinguish between accurate and less accurate ideas.

In 1998, a topographical survey was carried out using conventional means (tape measure, string, protractor) and from this the sketch of the Unterstetten Erdstall was made. This shows the extent in length (37m) and depth (7m). The floor plan shows the arrangement around the auxiliary construction shaft, the elevation shows the different levels of the rooms with descent and ascent through the 40cm loopholes. The Erdstall is without air supply ducts and can only be accessed from room 1. The current entrance is the one that led to the discovery of the Erdstall in 1993, the location of the original entrance is probably 1-2m southwest of it.

In the 3D scan, the seven rooms, the connecting hatches and the current access shaft can be seen. The arrangement around a central hole can be clearly seen. During construction, the auxiliary construction shaft was located there, from which the adjacent rooms were dug. Then, the rooms were connected by the slips and finally the auxiliary construction shaft with the excavated material was buried again. Thus, the only path left is the path over the successively lined rooms and connecting gaps.

The general view of the site shows the above-ground landscape, the construction trailer, the cars and the location of the underground Erdstall. It was constructed below the residential building: in recent decades, soil had been excavated from this area to be used for other construction projects. The overview was compiled from several individual scans using a Leica BLK360 LiDAR scanner. This clearly illustrates the spatial relationship between the current surface and the hidden underground structures.

MOBES - Mobile Erdstall Scanner: A hand-guided mobile device that captures 3D measurement data of the structure with RGB colour values for each measurement point in the confines of the Erdstall and slips through a combination of several measurement methods (stereo of motion, telemetry, LiDAR, gyroscopes) by scanning the surface. Recording sequences of the individual rooms are combined into an overall model by overlapping areas.

The measurement data from MOBES were used to make 3D prints of the model of the Unterstetten Erdstall. These vividly show the relationships and arrangements of the seven rooms and six connecting loopholes. The model also shows the position of the central auxiliary construction shaft.

The 3D scan of the entire Erdstall revealed recesses on the inside of the hatch from room 2 towards room 1, suggesting the use of a safety door. This door is supported against the opposite wall (there are two corresponding niches). In addition, a small recess remains free, through which an intruder can be prevented from advancing by means of a lance.

A special feature is the capstone in room 5: This is larger than the slip diameter to room 4. This can be placed on the slip, then additionally weighted down with body weight and bracing against the ceiling of room 5. This means that it is not possible for intruders from room 4 to room 5 above to overcome this obstacle in a short time. Persons from room 5 onwards are thus protected.