[Baron Munchausen]

1) A great 'cycle' of civilization. In the case of Foundation it was a specific course of history predicted by 'Psychohistory' while in Star Wars it was this constant oscillating between rule by the Jedi and rule by the Sith.

2) Secret or semi-secret societies with super-human powers ruling known civilization. In Asimov's case it was the "Foundation" itself. In Star Wars it was the Jedi/Sith.

3) Hugely developed capital world where the surface is actually completely covered and no longer accessible. Trantor/Coruscant

I suspect that I could go into more detail if I wanted to re-read the series.