Congrats, and nice find!

I know about these buttons. I actually uploaded a video to YouTube about it years ago. At the time it reminded me of the black monolith in Stanley Kubrick's "2001: A Space Odyssey (1968), so I called the video something like "Monolith at the edge of the world". But like you, I do not know what they're supposed to do elsewhere on the map. Yes, it would be great to figure that one out as well. I haven't visited that location in years, but I would be able to find it again.

If you're interested in trying to find a much more hidden secret, the only secret (that I know about) I've yet to figure out is the mystery surrounding the Starcrown Aerospace buttons. They're located up on the mountains surrounding the map (you can see how to reach them in my secrets guide) and either pressing them or pressing them in a certain way is supposed to change something somewhere in the map.

What that is, I don't know. So it's kind of a reverse situation to what this one was. Where I know how to activate it just not what it is that's been activated.

You are welcome! And a big thank you to you for bringing this to our attention. If you hadn't asked about it in the in-game chat area, my friends and I wouldn't have asked around and gone looking for it. :)