The Fort in Haarlemmerliede is a part of the Defence Line which extends 135KM around Amsterdam. The Defence Line was constructed between 1883 and 1920, and is unique in that it is the only defence system which controls the flow of water to achieve its goal. The defence line is designed to direct the water away from populated land in times of peace, and flood strategic points just enough to make them impassable in times of war.
