[clarification needed] Established on the border of Flanders, it was part of a double-line of fortified towns between Gravelines, Dunkirk and Maubeuge-Rocroi.
From Lille, Vauban supervised the construction of the many citadels and canals of the North, which controlled the border between France and Belgium.
Lille was taken from Spain by French troops in August 1667, and Louis XIV immediately ordered the construction of a fortress.
In 1671, the citadel became operational while Vauban continued to shape the city by constructing, a few steps away, a new neighborhood around the Rue Royale.
This allowed the use of swamp water and mud as a natural defense to make conditions more difficult for any possible enemy besieging the citadel.