The highway’s first head clings to the mountain’s northern face much like a remora clings to a shark. Its face is a mess of steel teeth that have been worn down over the centuries, drills and grindstones that process its host’s tectonic body into liquid stone. Rust and weathering have rendered this process imperfect, and waterfalls of wet concrete drool forth from its mandibles.

From above, its long, serpentine body appears solid, stable, and fixed in place; however, there is much activity to be found beneath all that gray skin. Miles of Archimedean screws churn the cement that it has swallowed, carrying it slowly eastward through ancient intrels. Pits of gravel along its flanks are the only evidence of its gradual motion, as well as of its once-per-decade molting process.

Its second head is much more difficult to find. Travellers who follow its length for several days eventually find themselves in a quiet city that has long since been strangled by its own main expressway. Its skyscrapers have been wrapped in stone like boa constrictors, and many of its smaller streets appear to have been thoroughly cannibalized. Here, it curls on itself in vertical loops that nothing with wheels or legs could ever follow. It seems only interested in being traversed by itself.

Eventually, the road leads out of the city. Some who have been to its end claim that the second head can be found overlooking a sea cliff, vomiting its pale contents into a careless ocean. Others, however, claim that it is a much more ambitious beast, and has recently begun sculpting a mountain of its own.

Every highway of sufficient length eventually arrives at the end of the world.

Self-constructing machines are also, on some level, self-destructive.