Like the Waterlinie, the Stelling van Amsterdam (Defense line of Amsterdam) is a defensive work consisting of mainly water engineering works, supplemented by forts where higher dikes, rivers or railroads would breach the inundated area.

The 135 km long defense line used mainly existing dikes, supplemented by new ones, and used a system of sluices and dams to allow a circle around 15-20 km from the center of Amsterdam to be inundated. In times of war the area around the capital could be sealed off and still support its population. It was built between 1880 and 1920, and is still (mostly) intact, largely thanks to the fact that until 1963 it was still officially military property.

In 1996 it was added to the list of UNESCO World Heritage Sites. (Note that the description on that page is highly confusing since it claims it is “the only example of a fortification based on the principle of controlling the waters” – which it isn’t. The Waterlinie is another example, and an older one at that.)

There is also a very informative website about the Defense Line of Amsterdam – much more than a summary (as suggested by the text “English Summary” top left).