The remains of the Castle can be visited
Freudenau Castle

The Freudenau castle ruin in Untersiggenthal, in the Swiss canton of Aargau, was a lowland castle. Its location on the right bank of the Aare, near the confluence of the Limmat, Reuss, and Aare rivers, made it a central point for goods traffic.
History+
Around 1240, a bridge was built over the Aare in Freudenau, intended to be protected by the newly erected Freudenau Castle. At this point, land routes and waterways from Bern, Lucerne, and Zurich to Basel intersected. The castle's numerous cellars suggest it served as a transshipment point between river and land transport.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Ruine_Freudenau_01.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 47.5124, 8.2340