Situated on the Dutch-Belgian border at one of the only strategically viable invasion points along the border, the fort was built up in WWII to defend against Germans attacking from the Dutch side of the crossing. The fort consisted of 17 separate bunkers and a number of support buildings, all of which was spread across 750,000 square yards of land making it one of the largest military forts in Europe at the time. The bunkers were connected by miles of tunnels that created a small underground city which not only made it harder to attack from the outside, but also ideal for defense against a prolonged siege.