Happened to catch this website which shows national boundaries over the last 5,000 years in 1 year increments - thought I would pass it along. As a history major, it is quite fascinating.
by year, since 3000 BC. Universal History datasets. Relevant Universal History vector information.
geacron.com
Things to note for context. First, it's only in about the 1600s that the modern concept of the nation-state existed. Before then, at least in the West, land was ultimately property of a lord, who got it from a string of liege lords, who ultimately got it from a monarch, who got it from God by virtue of being a monarch. So borders were actually borders of the lands nobles inherited through various and sundry marriages, inheritences, and so forth.
Before THAT, Rome was Rome. And so was the Byzantine Empire, which was never called that until some German came up with that alternate term for the Eastern Roman Empire centuries later. But in a lot of other places, there were really no fixed borders, just areas where different tribes lived at a given time until other tribes pushed them out or they moved. That's why the Hungarians ended up in Hungary after originating somewhere around the Urals. And the Celts ended up in Britain after originating somewhere around the Alps. And the Visigoths ended up founding a kingdom in Spain after originating somewhere in Ukraine or Romania. And how a Scandinavian tribe ended up founding what ultimately became the Tsardom of Russia.