Two favourite passages from Italo Calvino's Invisible Cities:
(From the introduction to section 9)
And from the mixture of those two cities a third emerged, which might be called San Francisco and which spans the Golden Gate and the bay with long, light bridges and sends open trams climbing its steep streets, and which might blossom as capital of the Pacific a millennium hence, after the long siege of three hundred years that would lead the races of the yellow and the black and the red to fuse with the surviving descendants of the whites in an empire more vast than the Great Khan's.
(From Cities & The Dead 5)
[...] you must think that the number of the unborn is far greater than the total of all the living and all the dead, and then in every pore of the stone there are invisible hordes, jammed on the funnel-sides as in the stands of a stadium, and since with each generation Laudomia's descendants are multipled, every funnel contains hundreds of other funnels each with millions of persons who are to be born, thrusting their necks out and opening their mouths to escape suffocation.