Den Oever is one of the two defensive positions on the Afsluitdijk (Closure-dike). On the photo is casemate number IX, armed with three MGs and an observation turret. You can see a MG embrasure that fires rearwards. On the right is toilet which could be used in peace-time. The thick concrete wall on the foreground has two purposes. It prevented heavy shells from hitting the foundations of the casemate. It also provided cover for the open position around the casemate. These positions had to cover the dead angles where the MGs in the casemates could fire. On the left you can see a joint. Since concrete shrink when it gets hard. Therefore it was built in two parts.

In 1932 the so-called Afsluitdijk was finished. This 30 km long dam closed the Markerzee, creating a large lake. It linked the provinces of North Holland and Friesland. However an enemy (read Germany) could also use the dike to attack Amsterdam from the north. That's why the dike received a heavy defense of two positions with a total of 30 casemates, costing 2.215.000 guilders, an huge amount for those days. To give an idea for the same amount they could built 527 armoured turrets or more than 1.500 small casemates.