The counts of Flanders’ quintessential 12th-century stone castle comes complete with moat, turrets and arrow slits. It’s all the more remarkable considering that during the 19th century the site was converted into a cotton mill. Meticulously restored since, the interior sports the odd suit of armour, a guillotine and torture devices. The relative lack of furnishings is compensated with a hand-held 45-minute movie guide, which sets a tongue-in-cheek historical costumed drama in the rooms, prison pit and battlements.
If you just want a photo of the castle, there's a great viewpoint on St-Widostraat.