The belfry came first - by more than five hundred years. Renaud I, count of Dammartin, commissioned it in the late twelfth century as part of the residence of the Counts of Boulogne. It was, in essence, the count's dungeon - the keep tower of his urban castle, his private symbol of judicial and fiscal power over the town. When Boulogne joined the royal domain in the late fifteenth century, the count's residence was repurposed for the common business of the burghers; the dungeon became the town's belfry. In 2005, UNESCO designated it part of a single World Heritage cluster of fifty-six belfries of Belgium and France, all in northeastern France and the Low Countries, all witnesses to the medieval rise of municipal power against feudal lords. The original spire burned down in 1712. Etienne Martinet replaced it with the octagonal capping tower that still crowns the structure today, finished in 1734.

By the early 1730s, the old town hall had become dilapidated. The mayor, Achille Mutinot, laid the foundation stone of a new building on 7 April 1734. Etienne Martinet - the same architect rebuilding the belfry tower - designed the new hall in a restrained neoclassical style: red brick with pale stone dressings, originally only six bays wide along the place. The interior held the Bureau du Maire, the mayor's parlour, and the Salle des Gouverneurs - a Rococo room decorated with portraits of Antoine d'Aumont, 1st Duke of Aumont, and his five successors as governors of the town. The building was a modest two storeys with a large attic. It has been added to twice since: an extra bay and an extra floor between 1854 and 1857 under Albert Debayser, who added the Doric porch and balcony to balance the facade, and an east wing by Pierre Drobecq opened in October 1934.

The paintings inside the hall tell stories the building cannot. In the Salle des Fetes, an enormous canvas by Claudius Jacquand shows the mayor Antoine Eurvin refusing to sign Boulogne's surrender to Henry VIII's English army during the siege of 1544. Another painting, by Francois Schommer, commemorates the visit of President Sadi Carnot in 1889 - five years before he was assassinated in Lyon. A third, by the lyrical-abstraction painter Georges Mathieu (a son of Boulogne, born 1921), depicts the medieval Battle of Tiberias, painted in 1958 and installed permanently in the hall in 1992. The paintings are political theatre: a city telling itself stories about resisting English kings, welcoming French presidents, and venerating its native artists - all in the room where the council still meets.

Boulogne's twentieth-century hour came on 22 September 1944, when the 3rd Canadian Division liberated the town as part of Operation Wellhit. The city had been catastrophically damaged - four years earlier the Battle of Boulogne had ended with Stukas demolishing block after block; in the four years between, German occupiers had ringed the town with Atlantic Wall fortifications, and Allied bombing had levelled much of what remained. The town hall survived. In August 1945, General Charles de Gaulle was welcomed inside by the mayor, Henri Henneguelle. De Gaulle returned in September 1959, this time as President of France, and went back into the same building. The post-war French Republic, the medieval county and the eighteenth-century municipality have all shared this address.

Today the belfry is open to visitors. The climb is steep - this was a thirteenth-century dungeon, not a tourist attraction - but at the top the view rewards everything below. To the west, the basilica's enormous dome. To the south, the cobbled streets of the Haute Ville and the line of complete medieval walls Philippe Hurepel rebuilt in the 1220s. To the east, the chateau-musee at the corner of those walls. Down below, the brick city hall steps out into the square named for Godfrey of Bouillon - the man who, with his brother Baldwin, took Jerusalem in 1099 and is buried, by his own account, beside the Holy Sepulchre. From an octagonal tower in a small French port, you can almost see the whole sweep of Boulogne's long argument with the world.