[Tagging] artificial cave, historic military shelter

[Martin Koppenhoefer]

sent from a phone

> Il giorno 04 set 2016, alle ore 11:40, Richard <ricoz.osm at gmail.com> ha scritto:
> 
> Also, I would 
> argue that "natural" implies natural


ok, agreed



> and there have been enough informal 
> proposals for man_made=shaft and similar.


I think a shaft is pretty different from those grottoes I mentioned, in being a vertical, regular structure and normally longer, while the artificial, decorative/recreational grottoes are not very deep. Also the former is usually of technical character, while the latter is decorative.

maybe man_made=grotto for these cases?

cheers,
Martin