Extensive excavations carried out in 1952 revealed the ruins of this gateway dating from the 16C. As it was also a watergate, it stood above a navigable tunnel giving access to a military harbour. From the top of the nearby ramparts, you will notice the step gable and octagonal turret of an old sanctuary of the Abbey of the Dunes, the ruins of which are in Belgium. This sanctuary houses a local history museum, the Streekmuseum "De Vier Ambachten".