Hidden in the Oostvoorne dunes is the so-called 'Biberbunker'. This St-type L487, codename 'Bertha', was built to function as a radar command post for the German ari force. The bunker has since been set up as a museum and demonstrates how the command bunker worked. Guided tours of the bunker are available on Bunkerdag, the last one of the day commencing at 17:00.
In addition to the guidance of German fighters, all FLAKs (anti-aircraft cannons) were also provided with up-to-date altitudes and flight path information from here. A special Bunkerdag treat this year is the presentation of an entire FLAK, installed in its original bedding directly opposite the Biberbunker.