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.
It was fascinating to see the shiny copper oxidize over a relatively short space of time.
https://www.rathaus.bremen.de/rathausdachsanierung-2016-3196...