Le Quesnoy was fortified as early as 1150, with a castle and ramparts holding the first enclosure that consisted of crenellated walls, guard walk and circular towers. The first fortifications were partly replaced by a new enclosure in 1533 when the town was under Spanish rule. The town was besieged on several occasions by the French and the Dutch, until the time of Louis XIV, when it was re-attached to France for good under the 1659 Treaty of the Pyrenees. The first work to be done was the restoration of the stronghold. Things changed again when Vauban came along in 1668. He kept four bastions dating from the era of Charles V and built four new ones, to add Le Quesnoy to the front line of the famous "Pré Carré" in 1678. The complex, which has remained intact, is listed as an "Historic Monument", and there is a 12-kilometre circuit taking you through to wonder at the quality and ingenuosity of these fortified buildings, particularly the ditch-flooding system.