The Droogdok Jan Blanken is the oldest surviving dry dock in the Netherlands and one of the best-preserved in Europe. Built in the early 19th century, it is a remarkable piece of hydraulic engineering — a large enclosed basin that could be pumped dry to allow ships to be hauled out for repair without having to be beached or tilted. The scale of it is impressive even today.
The dock is now a national monument and open to visitors. The surrounding naval yard contains several other historic structures, including warehouses, a forge, and the machinery used to operate the dock gates. The whole complex gives a vivid sense of what a major naval facility looked like in the age of sail and early steam. There is a small interpretive display but the dock itself, and the ability to walk around and through it, is the main draw.