After laying siege to Laon, Henri IV ordered the construction of the citadel in 1594, as a reprisal against the town itself, destroying the plain district, Notre-Dame-au-marché church and Saint Georges church. The work directed by Antoine Etienne was completed in 1598, the year in which the governor took possession of the city. At the end of the reign of Louis XIV, the city was demilitarized and abandoned to the retreating military, and a redevelopment of its fortifications began under Louis-Philippe in the mid-19th century. * During the First World War, the citadel was occupied by German troops and used as a cantonment camp and hospital. It should be noted that the citadel premises are not open to visitors, unlike its underground passages, where the ‘Secrets beneath the city’ tour takes place daily! (For practical details, please contact the Tourist Office).