The Stelling van Amsterdam (Defence Line of Amsterdam) is a 135 kilometers long ring of fortifications around Amsterdam. It was built between 1883 and 1920 and consisted of 46 armed forts and batteries, acting in concert with an intricate system of dikes, sluices, canals and inundation polders. It is a major example of a fortification based on the principle of temporary flooding of the land, aimed at protecting the Dutch capital against a possible foreign attack. The Stelling van Amsterdam is listed as a UNESCO World Heritage site since 1996.

The Fort bij Spijkerboor is the largest of the 46 fortresses, located in the Beemster Polder. The fort was built between 1889 and 1911 to defend the Northern Front. It was one of the most modern and heavily armed forts of the Defence Line of Amsterdam, equipped with an armoured turret with a double-barrel 10.5-centimetre cannon. The fort has two storeys because of the height of the dike to be defended. The fort was mobilized during the World War I. At that time there were 300 soldiers stationed. Although this defensive structure remained in the possession of the Dutch army until 1975, it has been mainly used as a prison throughout the years. Over the course of time, inmates have left their mark in the form of beautiful murals. At the heart of the fortress is a chapel, featuring these decorations.

Fort bij Spijkerboor can be visited and is a kind of musuem, showing how the soldiers lived there with sleeping quarters, laundry rooms, an army kitchen with huge boilers and even a private loo for the officers !!