This is North-West-Cental Europe. It it an area exactly 1,000 miles from North to South, and 1,000 miles from East to West.
Think of what comes to your mind when you hear “The Middle Ages”. Unless you have a specific, personal interest in medieval Spain, Ireland, or Russia, almost everything that you think of will have been within this area, with the one notable exception of the Crusades. Even the vast majority of all Viking stuff.
Historians generally place the Middle Ages in roughly the time from 500 to 1,500 CE, which happens to coincide with the disappearance of the Roman Empire in Western Europe, and the discovery of America and the Reformation. So it all also falls into a span of 1,000 years.
A thousand miles and a thousand years. That’s the Middle Ages as a setting for popular fiction and reference frame for Fantasy. Compared to many popular fantasy settings, that’s tiny. But there’s so much stuff in this little box. More space than you could ever possibly need to tell your stories. It certainly won’t hurt if you can give names to the distant lands that lie beyond the edges of the map, where merchants get the most exotic of their goods. But to characters dealing with their own lives inside of this box, they don’t need to be anything more than that. Things are of course different for campaigns about traveling to far away exotic lands, which certainly have their place in fantasy. But those really are the exception, not the rule.
My current campaign is coming up to the 200 hours of actual play mark, and has covered over four years of game time. In all that time, the PCs have never left an area of roughly 240 by 160 miles – approximately the size of Switzerland. As long as an area is ‘sticky’ enough, and has enough *stuff* going on in it, even a very small geographical zone can provide material for adventure more or less indefinitely!
That’s certainly another good point. Time and distance in fiction, particularly in RPGs, really are unit-less anyway. Unless it’s a campaign which has armies or rival parties of adventurers racing across the landscape to reach certain places first, game settings don’t really have dimensions. Buildings, dungeons, and caves are their own self-contained universes and movement between them is basically instantly, with maybe the occasional quick break in a clearing to have an encounter.
RPGs don’t really have a physical overworld. What they need is a believable illusion of such an overworld. But that illusion can actually be really flimsy. Like the map for The Lord of the Rings shows lands in the far north, the northeast, and the south. While the creator had some ideas for what these places are like and their history, they never actually come up in the text itself.
I very often see people proudly announcing that they are building a world and showing their fancy giant maps to cover an entire globe, and then having questions about how to fill all that with content. While I sometimes feel grumpy about Forgotten Realms being reduced to only the North and the Sword Coast in the last 14 years, it’s also a much better precedent for players as of how big a big setting actually is. In hindsight, that giant map of Faerûn was a big mistake. About two thirds of that continent was never actually used in any published material.