>> folklore?

Well that's certainly one indicator, but in each instance it should carry a dubious flag if the lore isn't 1000+ years old (or longer probably).

>> proximity to other actual megalithic sites?

That's my favourite reason, but the site should probably be added as a subsite of the 'real deal', which paradoxically is probably the wrong way around if the rock is an older place of importance.

>> vibes? because I say so?!

Surely they are the same thing in most cases? Probably not a good reason, but if 'feel the vibes man!' isn't involved and a good argument is presented (along with a dubious flag) then perhaps it should be posted so that others can commment.

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Obviously the above are just thoughts