I have not yet read much of Neal Stephenson's Anathem, although it has insistently dragged itself close to the top of my "read me" list, with only two half-read books ahead of it. I have dipped into it, and can see how the machines in my previous post might, as Steve Muhlberger suggests, evoke the gigantic Great Clocks of the novel, designed to keep time over millennia.
The Long Now Foundation is one of the inspirations for the clocks in the novel, and has produced a prototype for the clock, an orerry and chimes. The foundation hopes to build their clocks on a monumental scale with the works buried underground.
Beautiful machines, but not, I think, as charming as what I think of as Millennium Clock 1.0, the Prague Astronomical Clock or Prague Orloj. It recently celebrated its 600th anniversary, and is more than halfway through its first millennium.
The Orloj has stopped several times since it was made, and each time, it has been repaired. Most recently it succumbed to German shelling during the Prague Uprising of 1945. They fixed it afterward, because it was so wonderful. It has outlived several states that claimed Prague as their capital.
If you want to build for the Long Now, then build something awesome, build something beautiful. Later generations will fix it when it breaks.