In the first part of "End of Eternity" it seems like Eternity is off in a separate plane of reality, disconnected from time. But then later it explains how each section was duplicated for each century and implies that each section is actually in it's century. This is reinforced by the narrative of Harlan traveling up and down via kettle to the far future where he has Noys staying, and contemplating vast empty centuries on either side. But on the other hand, it seems that they can travel via kettle to different places within a century, so what's the value of having the section actually in the century it works on?
So I am a bit confused as to the nature of Eternity. Is it series of real places, one per century, and the thing that makes it "Eternity" is simply access to Kettle and knowledge of how to manipulate time? Or is it some place off outside the normal universe and time? Or possibly did Asimov make it confusing on purpose?