What borders in Europe are inevitable and which are not inevitable?

[ook]

Czechia and Moldavia borders are not along the Carpathian range.
Anyway administrative divisions of Ukraine and Romania still go around it.

Western parts of Carpathian range are actually located in Czechia and parts of it forms border between Czechia and Slovakia, and used to be borders between Czech kingdom and Hungary.

Also, I found a video which roughly shows how borders of Czechia changed through history. You can exactly see that mountains around Czech republic were very important.

 

[Petike]

Czechia

Which is why my country's natural borders with Czechia consist primarily of the White Carpathians.

 

[Gloss]

Which is why my country's natural borders with Czechia consist primarily of the White Carpathians.

Lel, I thought you were referring to the other Czech ranges.

 

[Gloss]

Western parts of Carpathian range are actually located in Czechia and parts of it forms border between Czechia and Slovakia, and used to be borders between Czech kingdom and Hungary.

Also, I found a video which roughly shows how borders of Czechia changed through history. You can exactly see that mountains around Czech republic were very important.

Yes but only the White Carpathians are actually Carpathians, the other aren´t.

 

[ook]

Yes but only the White Carpathians are actually Carpathians, the other aren´t.

You wrote that Czech borders are not along Carpathian range, which is not correct. Whole eastern border of Czechia is along Carpathian range.

 

[Gloss]

You wrote that Czech borders are not along Carpathian range, which is not correct. Whole eastern border of Czechia is along Carpathian range.

Not really but is true that the Carpathians continue along most of the Czech-Slovak borders.

 

[WeissRaben]

For much of the last millennium, at least parts of both sides of the Alps were notionally within the same polities. They were still felt like a border, though. Remarkably, the holdings of the House of Savoy consistently straddled the main mountain chain from the eleventh century until 1861 (they got important controlling the passes initially) and this happened initially exactly where the Alps are get the highest.
This is also sorta true of Tyrol until 1918 (and with a parenthesis during WWII).

On the other hand, the Aosta Valley, Ticino, Valtellina, and Trentino are the largest valleys across the highest mountain range in Europe; countries controlling them (or trying to) to feast on tolls is neither unexpected, nor makes the Alpine watershed less of a natural border.

 

[Saphroneth]

If the Rhine were the border it would be seen as a natural and inevitable border.
But it's not.
So I think any guess at natural borders is difficult.