Catholic - Protestant border in NL still at the Roman frontier
A statistical boundary between Nijmegen and Arnhem, The Netherlands, divides a Roman-Catholic south and a Protestant north.
This is smack on the line that was the boundary achieved by the Roman empire — the "great rivers" having been the northern Continental border of their huge civilization — and of their religion.
The great rivers of today (they shift in delta sand and clay, changing course in historic timescales) run westward past Arnhem and Nijmegen. These paired cities are about 20 km north and south of each other and equidistant from where the Rhine (Rijn) first splits, just inside The Netherlands' border.
For the Romans, Nijmegen was the frontier. They imposed themselves up to this bank of the river — or, more accurately, to this side of the great rivers.
Beyond were the Germanics, and although the two peoples conducted extensive business, the cultural border lasted for the duration of the Roman empire.
The language hasn't held that firmly, though it's not far off. Belgium, just south, is bilingual — Latinate (French) and Germanic (Vlaams [Flemish,]) a form of Dutch.
* Holland is one of the most secular countries in the world. You don't see people in the streets over religious differences.
(A notable exception was the 1985 papal visit, when Utrecht fell into violence. But that was a protest against a religion — and an expression of popular condemnation of that religion's policies.)
No Protestant-Catholic disagreement rises to the level of embattled dispute, as it has, for example, in recent years in Ireland.
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