> sits in the center of England where its diameter is at its narrowest
Seems like a good place to put a wall to split the land in two then. I wasn't aware until just now that the modern border of scotland is a good bit north of where Hadrian's wall is.
Hadrian's gets all the recognition, and that's probably mostly because it is still recognisable, but the Romans built a second wall 20 years later, just to the north of where Glasgow and Edinburgh are now - https://en.wikipedia.org/wiki/Antonine_Wall
It was built mostly of turf and wood, so time has erased it much more completely, and apparently they retreated back to Hadrian's wall after only a few years.
That might be another reason that Hadrian's Wall is more remembered - It's one they held for a reasonably long time (generations) whereas Antonine's was far more ephemeral in that way too.
The Berlin Wall is almost gone, but I don't think anyone will forget it in a hurry.
Seems like a good place to put a wall to split the land in two then. I wasn't aware until just now that the modern border of scotland is a good bit north of where Hadrian's wall is.