It is interesting to me that a good chunk of Western Europe was already united once before and fell apart again. You only really realize how large the territory he ruled over was when you find out in how many languages they have a localized name for him and that in general the impression was not so much of a conqueror (which he definitely was) but a uniter. And it's well over a thousand years ago.

edit: Oh, another funny thing: To this day there are people trying to trace their family linkage with Charlemagne, or "Karel De Grote" as he's called here.