Quote Originally Posted by lars573
It might be better to say that the institution of Holy Roman Emperor and King in Germany (which is what the full title was) lasted for 1000 years.
The term "Sacrum Imperium Romanum" wasn't used until Otto the Great, though I'm not sure about the date. Till then it was simply "emperor". At any rate, though the structure and titelature of the german empire evolved over time, we can trace the history of the HRE back to the treaty of Verdun.

I'm surprised no one has mentioned universities, though I do wonder if they fit into "social, economic or political".
Good point about the universities. I forgot about them.

Another thing that might deserve mention is the legalistic works of the Byzantine emperor Justinian (or rather that of his minister Tribonian). Established in its final version in 533 it was used in Greece in different translations till 1946, and it was used widely throughout Europe as law governing international relations till replaced by national codices, as a primitive form of international law you might say.