This 14th century tower is one of the few remains of the medieval French outer castle defence. The Artillery Tower (Artillerietoren) or Armoury Tower was built along with the castle in 1301-1302 by the French King Philip the Fair, as part of the French-Flemish war against the Count of Flanders. The tower was located at a strategic point between the city moats and the castle moat. It was originally intended for use as a drinking water tower. The Artillery Tower was part of the fortifications surrounding the Church of Our Lady. It was later converted to a storage depot for cannons and later still served as a place for making and storing gunpowder and munitions. The tower is classed as a historic monument.