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Is cave exploration an indoor or an outdoor activity?
(infosec.pub)
A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. A showerthought should offer a unique perspective on an ordinary part of life.
I'm going to say outdoor.
The "door" part doesn't really have any significance. No one would say camping under the open sky is an indoor activity, even if there's a fence with a door around the campsite.
I think it makes more sense for the deciding factor be whether you're in a controlled or uncontrolled environment. And while part of the cave might be controlled if there's an artificial entryway or home, that's not what you're there to see.
Maybe I'm gatekeeping, but isn't a fence door a gate?
I’ve been in show caves in Bonaire that had some degree of climate control, mainly for humidity and to ensure sufficient oxygen for visitors for a comfortable experience and to accommodate large groups.
Certainly that’s the exception rather than the rule in my case.