consists of two interconnected forts of the Defense Line of Amsterdam, constructed to defend some accesses (Slaperdijk, Spaarndamseweg) and the Spaarne. The building of the earthworks began in 1886.
The form. Fort Noorden Spaarndam (Nieuwe Rijweg approx.) and the Voorm. fort bezuiden Spaarndam (Boezemkade approx.) both have a defendable earthwork (1895) and an elongated bomb-free main and front building (1901) with observation dome and flanking separate lifting domes. At the northern fort there is a secondary battery (1903). There is a line wall with front moat between both forts. For reinforcement, a new canal with a moat was constructed on the west side in 1917-18, with machine gun arrangements and a large number of concrete group shelters between the two lines.
