Almost nothing remains of Unspunnen Castle beyond a single ruined tower on a wooded knoll above Wilderswil, about three kilometres south of Interlaken. The walk up from the village takes fifteen minutes through forest. What survives is evocative rather than spectacular — a mossy stump of medieval masonry looking down on a valley that has changed considerably since the 12th century. The views south towards the mountains are good.
The castle's main claim on attention is the festival it has lent its name to: the Unspunnenfest, a celebration of Alpine folk traditions held roughly every twelve years in Interlaken. The programme centres on traditional wrestling (Schwingen), alphorn playing, flag-throwing, and the famous Unspunnen stone-throw — a test of brute strength dating to 1805, when the festival was invented as a gesture of national unity in the wake of Napoleonic occupation. The next festival is worth planning around if you can manage the timing.