[Tagging] Mapping cave tunnels passable by human

[Pieren]

I'm afraid that the main problem here is not the use "location" or
"layer" or "cave" but "highway=path". This tag was created for
multiple vehicles ways, not exclusive to a transportation like
footways or cycleways. Currently the wiki tries to reflect this in the
"path" definition:

"A route open to the public which is not intended for motor vehicles,
unless so tagged separately. This includes snowmobile trails, ski
trails, hiking trails, horse trails, bike trails and paths, mountain
bike trails as well as combinations of the above and other modes of
transportation. "

Unfortunatelly, this tag was abusively (impov) reused later for
climbing routes. And now for caving. But none of these activities are
open to the main public, requires special skills and equipments (incl.
for survey) and, as already mentionned, needs a better handling of
elevation data which is not easy in our model. I'm afraid that the
main reason to not create new "highway" tags was/is to see them
immediately on the rendered maps...

That's why I would prefer something new like "highway=cave" (or
whatever you like) without any additional mandatory tags like
"location=underground" (correct me if I'm wrong but a cave is always
underground). That would not be immediately visible on the map but
data consumers requesting "all highway path in Poland" could also
safely ignore this creation.

Pieren