Not really what you're asking for, and I can't find the project anymore (I think it's the search engines? I used to be good at this.) Anyway, there's a guy wh

Not really what you're asking for, and I can't find the project anymore (I think it's the search engines? I used to be good at this.) Anyway, there's a guy who etches data into ceramic discs and stores them in a cave or old mine in, um, I want to say Switzerland?. The discs themselves would conceivably last millions of years, and barring cave-in of the tunnels they're stored in, uh, yeah.