The Belfry of Thuin is the town's anchor: a 17th-century tower on Place du Chapitre and one of the Belgian belfries included in the UNESCO World Heritage listing. It is not huge, but it has the civic self-confidence that makes Belgian belfries interesting in the first place.
Climb it for the view across the Sambre valley and the tiled roofs of the upper town. If the tower is closed, the square beside it still gives a fine sense of Thuin's hilltop position.