There's another 'unsubstantiated', yet massive cairn upon South Black Hill in the Pentlands which, to me, makes no sense unless complementing the one on nearby Carnethy Hill
Guess the point is there just aren't enough 'official' resources to visit and note everything...
I do really like the look of Gladman's Cairn - to give it its now official title :-) on South Black Hill. The connection with the cairn on Carnethy Hill just felt strong when walking the hills between them. It's a mystery that I'd love to know the answer to.
Here's a view over the top of it. It's massive. Got to thank you again Gladman for posting the images of it a few years back. We've been lucky to have a few good days out there because of it.