Ancientness, Modernity And Futurity

The phrases, "ancient civilizations" and "modern machines," convey opposite, contradictory, antithetical connotations. (I think.) Yet sf writers imagine ancient civilizations with machines on other planets and in our future. It is to be hoped that such civilizations do and will exist - although, if there had been any in nearby planetary systems, then they should have been detected by now.

In 50,000 AD:

"They went through immense vaulted caverns hewed out of the rock, dank tunnels of silence where their footfalls echoed weirdly and shadows flitted beyond the dull glow of fluorospheres. Now and then they passed a looming monstrous bulk, the corroded hulk of some old machine."

-"Flight to Forever," p. 209. 

And see also Something Basic on the James Blish Appreciation blog.