Updated:
The Aare runs through the middle of Thun, past busy terraces and the old town’s unusual raised pavements. The castle is above you, the lake a little farther away. This is a proper town as well as a holiday stop, with shops to browse and plenty of reasons to stay for dinner.
For the old streets, head towards Obere Hauptgasse and Mühleplatz. For open space and the lake, choose Schadau Park.