Thuin is a small Walloon town that climbs sharply from the Sambre River to a compact upper town of stone lanes, old walls, gardens, and a belfry that belongs to the UNESCO-listed Belfries of Belgium and France. It is close enough to Charleroi for an easy half-day, but it feels much older and quieter than the industrial plain around it.
The upper town is the reason to come. From Place du Chapitre you can climb the belfry, look over the Sambre valley, then follow the paths through the hanging gardens on the south-facing slope. The old ramparts, Grand-Rue, and little viewpoints make Thuin a good place for unhurried wandering.
Thuin has one specialist draw that lifts it above many small Belgian towns: the ASVi tram museum, with historic Vicinal trams and operating heritage lines towards Lobbes. Add Aulne Abbey downstream and there is enough here for a rewarding day, especially if you like railways, medieval towns, or river walks.