Comment by cesarb

> The alien machinery hums along, producing polymers. [...] The more I look around, the more the engineering world, once you go back more than a few years, looks like subterranean New York City. A mass of strange engineering feats humming away out of sight, produced by long-forgotten ancient peoples

These sentences made me think of the game Factorio. For those who don't know, in the original game (before the recent Space Age expansion) the official objective was to build and launch a rocket, leaving behind the still running automated factory which produced the parts for that rocket (and yes, one of the intermediate products is polymers, simplified in the game as "Plastic"). One can imagine someone, much later, encountering the long abandoned factory, still running and still producing polymers.