In 1672, when the French King, Louis XIV, invaded the Dutch Republic, Naarden was quickly captured. But, at the very last minute, the Dutch breached the dykes and flooded the land to the west of the town. This proved to be a smart move. The French were blocked by an impassable barrier of water and mud, and forced to withdraw. This was the beginning of the famous Old Dutch Waterline in which Naarden played a prominent role.
After the siege with Naarden back in Dutch hands, the fortifications were completely redesigned and Naarden took on its characteristic star shape. The new fortifications were completed in 1685. Since then, the fortress has remained virtually untouched.