Where was the capital of the Holy Roman Empire, at least until the mid-1400s? Can you go visit the remains, see a museum about the place?
Well, yes and no. Because there are and were many places that served as the center of government of the early forms of the Holy Roman Empire, ranging from Aachen in the west to Goslar in the east, to Frankfurt and down into the Black Forest, into Italy, even Sicily. The empire traveled with the Emperor, and the administrative staff and records went with him.
I’ve been to several of the imperial capitals, as long as they were north of the Alps. Aachen is probably the most famous since it was Charlemagne’s city and favorite place, and his church and throne are there, along with other, smaller relics.
However, he traveled almost constantly across the Frankish lands (France into Spain) the Saxon border areas, as far east as modern Austria, down to Rome several times…
After his direct line died out, the center of government activity shifted east and south, down along the Rhine and across the northern slope of the Alps. Later it bumped farther east, to Goslar and the Harz Mountains, because that was literally where the money was.
The Harz mining region was a major source of the silver and gold that paid for the Holy Roman Empire of the German Nations, later boosted by the silver and gold of Kutna Hora in Bohemia. But when the emperor traveled, the administrators all went with him. Not that there were very many, but still, your average early medieval noble is not really prepared to have several hundred nobles, priests, servants, and all their animals and baggage show up on short notice and stay for over a month.
Thus the institution of the pfalz. There’s not a good single English word to describe what a pfalz did. Perhaps depot comes close, but these were also administrative points, sort of local courts combined with silos and hotels and armories, but not quite that exactly. The pfalz was a place along a known travel route that provided for the needs of the imperial court, imperial couriers, and others, as well as serving as a temporary administrative center when needed to conduct imperial business. They were not castles, but could be strong points. In the later phases, once the Staufen family came to power for a few ears, they were generally about a day’s travel apart, sort of imperial inns, but more than that.
They declined in importance as an institution after the 1300s, and once the Habsburgs secured the title of Holy Roman Emperor after 1450 or so, the center if imperial power stayed in Vienna. With a notable exception – when a new emperor was elected, he was crowned in Aachen, then held court in Frankfurt, then visited Nuremberg before returning to Vienna. Imperial law required it, both as a tangible link to Charlemagne and the origins of the title, and as a reminder that the people of the empire had certain rights and could impose restrictions on the emperor if the need arose.