De Hoop (The Hope) is a corn mill standing within the old rampart circuit of Dokkum, one of two windmills that give the town its distinctive skyline. It's a grondzeiler (a mill set on the ground rather than a raised structure) and has been grinding grain on this site since the 18th century.
The mill is occasionally open to visitors, particularly on national mill days (the second Saturday of May, when most Dutch mills open). The interior gives a sense of the working machinery — the wooden cogwheels, millstones, and sack hoists that made these structures the industrial engines of pre-modern Friesland.
Even when closed, De Hoop is worth approaching for the view it gives of the canal ring — from the mill's base, you can see the circular pattern of the old fortifications particularly clearly.