The secret medieval tunnels that we still don't understand

Maybe they needed a place to store the dodecahedrons? https://en.wikipedia.org/wiki/Roman_dodecahedron

Based on just this article, it seems far most likely to me that it was a place to hide during an attack.

> And while three brave explorers in the 21st century once spent 48 hours in an erdstall, crawling to new sections whenever oxygen became scarce, it seems unlikely that they would have been constructed as hiding places, even temporary ones. Though they could have provided refuge for a small family, why would they be accessed from such public spaces?

I don't see why a whole bunch of people couldn't have hidden in them for several hours during an attack/raid? A hiding spot sufficiently known to a few, just big enough. And then it makes perfect sense the entrance would be in some central public place.

> The lack of exits is a further strike against this theory—if enemies became aware of such a tunnel being used as shelter, it would quickly become a death trap for its inhabitants.

Which would contribute to their extreme secrecy. And the loops and dead ends and narrow spots make it all the harder for attackers to pursue you even if they find it.

> Besides, in either of these cases, one would expect at least some goods to have been left behind—remnants of food or clothing, cached or dropped valuables. Instead, there is nothing.

If they were intended for hiding for just a few hours, since oxygen would run out anyways, it makes sense for nothing to be left in there. You rush in and come back out when the raiders have moved on. Clothing was valuable, you weren't going to leave your shawl behind.

Heinrich Kusch did some excellent work on this. Here[0] are some video documentaries. Some of his findings will blow your mind.

0. https://www.unterwelt-kusch.com/dokumentation/film-und-audio...

Is it possible they're the medieval equivalents of dry-wells? Why build something big-enough for people if all you want to do is accommodate run-off or sewage? What's the geology like; porous vs. no-porous? Porous enough for storm drainage, maybe? It seems a stretch to call them secret. Why document something as common as a drain?

Was there a populist (home) mining fad? People got excited about digging for possible resources and dug crude exploratory tunnels?

Maybe it was like a safe. If people wanted to steel something it would take them a very long time and they would be very easy to stop from ever coming out alive.

TIL hn will tell me about archeology just a bikeride from my office.

very fun!

Medieval children dug those for fun and games. Explains the size and lack of recorded attribution.

A lot of folks are latching on to the "hiding place" theory, and that could very well might have been one of the use cases. But as the article points out, the lack of a second exit makes that unlikely.

I would like to offer a competing theory. These are thermally stable storage places for perishables.

As heat transfer is directly proportional to surface area, the ideal vessel that maximizes the volume / surface area ratio would be a sphere (like some cryogenic tanks for rockets). But if you don't have the technology to make that or a cylinder, then the best you can do is observe that lowering surface area helps and make smaller, long rounded passages to try and optimize a ratio that you don't understand by feel.

I think it's more likely that these are are ancient fridges / hot boxes than a way to spiritually experience rebirth. I think a thousand places to store hay for horses and cheese for your family is far more likely.

Could these be boltholes? Yes, but how frequently were places getting invaded? War was mostly siege based and was fairly infrequent for a given city / place (i.e. even if the polity next door was under siege at the time. You weren't) Winter and summer - on the other hand - were and are yearly guarantees.

Hyperion, anyone?

Weren't people much smaller in those days? Maybe adult men could have fit just fine.

"passages become seemingly impossibly narrow, as small as 16 inches (40 centimetres) in diameter. "

Vs

"and the minimum width between armrests is 39.37 cm (15.5 inches)." https://help.ryanair.com/hc/en-us/articles/31352078107921-Se...

FTFA:

This clandestine treatment would have made sense had the erdstall been built as escape routes in case of invaders, but this can’t have been their purpose. They only ever have one entrance, usually located beneath the floor of a church or farmhouse, or simply under the flagstones of a town square.

That SCREAMS "hidey hole in case of invaders", to me. Like the hole Saddam Hussein was discovered hiding in.

If the countryside is overrun with invaders, there's literally no place for peasants to escape to. But if you can safely hide until dark, you have a chance. If you can wait out until the invaders pass through to their objective (strategic castle, opposing force...), you survive.

As people spent time in them, the oxygen would run out and be replaced with carbon dioxide, which is heavier than air and would sink to the bottom. With no exits and no airflow, wouldn't this become a straightforward deathtrap at some point? Or were there ways to force clean air to the bottom, somehow forcing out the CO2?

Reminds me of the film “The Borderlands”, won’t spoil anything but it’s a good bit of eldritch horror.

Tunnels through which dogs could carry packages or messages no matter what the weather was like and without fear of getting lost or interfered with on the way?

The chambers at the ends could have been where the dogs slept and were fed.