The Château de Bilstein is a ruined castle in the hills above the Riquewihr and Ribeauvillé wine country. It is not the easiest sight in the area, and that is the point: you come for a walk through forest and vineyard rather than a polished monument.
The remains are modest compared with the better-known castles above Ribeauvillé, but they add a good outdoor option if Riquewihr's main street feels too crowded. Wear proper shoes after rain; the hill paths can be slippery.