The Nevenbatterij Fort bij Penningsveer is one of several batteries which form a part of the defensive line which began construction at the end of the 19th century. The defence line took around 40 years to build, with the final pieces being put in place around 1920. The defence line protected the areas around Amsterdam, draining water from the land during peace-time, and flooding the land as a form of protection during war. The remaining forts and batteries are now national monuments.
