This is one of six forts making up the Den Helder defence line. Fully restored, nowadays it houses an exhibition and an aquarium. The guided tour along the underground passageways brings the history of the fort to life. In the blockhouses where the North Sea Aquarium is located, be sure to see the glass tunnel. From the fort, on a clear day, there is a beautiful view of the Razende Bol sandbank, the North Sea and the island of Texel.