Elfish underground caves in Bavaria

[Phidippides]

These are unusual.  Anyone visited them before?  According to the article they probably weren't used for food storage or for another "practical" purpose.  However, I wonder if they have considered how the tunnels may have been characteristically different during the medieval warm period....perhaps they didn't fill up with water as they do now.

The Greithanners, from the town of Glonn near Munich, are the owners of a strange subterranean landmark. A labyrinth of vaults known as an "Erdstall" runs underneath their property. It is at least 25 meters (82 feet) long and likely stems from the Middle Ages. Some believe that it was built as a dwelling for helpful goblins.
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At least 700 of these chambers have been found in Bavaria alone, along with about 500 in Austria. In the local vernacular, they have fanciful names such as "Schrazelloch" ("goblin hole") or "Alraunenhöhle" ("mandrake cave"). They were supposedly built by elves, and legend has it that gnomes lived inside. According to some sagas, they were parts of long escape tunnels from castles.

Hideouts or Sacred Spaces?
Experts Baffled by Mysterious Underground Chambers