Röstigraben

Röstigraben is a term used to refer to the cultural boundary between German-speaking Switzerland and Romandy, the French-speaking parts. There is also the term Polentagraben, referring to the boundary between German-speaking cantons and the Italian-speaking canton of Ticino.
The term first appeared during World War I, when neutral Switzerland stood between the warring German Empire and the French Republic.

Etymology

The first part of the term is derived from the Swiss German name for hashed potatoes, rösti, which originated in the canton of Bern and is considered typical of Swiss German cuisine.
Graben has both the concrete and abstract meaning of "rift", with the Saane/Sarine river valley in the bilingual canton of Fribourg separating the linguistic areas. The Swiss-French use a similar expression: barrière de rösti, literally "rösti barrier", or rideau de rösti "rösti curtain". Just like Röstigraben it has become a familiar facetious expression used whenever differences arise, e.g. different voting results.

Geographically the line stretches from the Jura Mountains in the north along Lake Biel, Lake Neuchâtel and Lake Morat through the Swiss Plateau, then crosses the Swiss Alps and the valley of Rhône, separating Lower and Upper Valais, and finally reaches the Italian border between the municipalities of Evolène and Zermatt. Folklorists emphasize the importance of the parallel Brünig-Napf-Reuss line further in the east, separating the historic Alemannic and Burgundian spheres of influence.
By analogy, the term Polentagraben is used to refer to cultural and political differences between Italian-speaking Ticino and German-speaking Switzerland. The canton of Ticino is seen as having a tougher stance towards migrant workers and a greater attachment to the notion of Swissness.