Around 1334, the Freiherr of Weissenau joined other local nobles in a war against the growing power of the city of Bern.

After the defeat of the nobles, Weissenau was forced to sell the castle and Widen to Interlaken Monastery to pay his debts.

In 1365, the monastery moved the weekly markets and yearly fair away from Widen and to the village of Aarmühle (which is now Interlaken).

[2] In 1528, the city of Bern adopted the new faith of the Protestant Reformation and began imposing it on the Bernese Oberland.

Weissenau Castle and the small village of Widen became a part of the Bernese bailiwick of Interlaken.