Boulogne has always been two towns. Up on the hill, the Haute Ville keeps its complete medieval curtain wall - rebuilt in the thirteenth century by Philippe Hurepel, count of Boulogne and son of King Philip II. You can still walk the full circuit. Inside the walls are the basilica, the chateau, the cobbled streets, the Hotel de Ville with its twelfth-century belfry. Down below, on the flats either side of the Liane, sprawls the Basse Ville - the working town of fishermen, brick warehouses, and the docks that make this France's leading fishing port by tonnage. The two are connected by steep ramps and stone staircases that climb out of the modern city straight into the Middle Ages.

On a quiet street in the Basse Ville sits a modest house known as the Casa San Martin. Jose de San Martin - the Argentine general who liberated Argentina, Chile and Peru from Spanish rule - lived his last two years here and died here in 1850. His body was kept in the basilica's crypt until 1880, when Buenos Aires finally brought him home. Simon Bolivar, his colleague in the South American revolutions, planned to come to this same coast in exile before his death in 1830. Boulogne's long ties to Argentina - reinforced by nineteenth-century emigration from Nord-Pas-de-Calais to South America - explain the Argentine flag that flies above the house and the statue of Bolivar that watches from a nearby square.

For a town of forty thousand, Boulogne has sent a remarkable number of people into history. Eustace II of Boulogne fought at Hastings in 1066. His grandsons Godfrey of Bouillon and Baldwin became kings of Jerusalem after the First Crusade. Matilda of Boulogne was queen consort of England in the twelfth century. The Egyptologist Auguste Mariette, born here in 1821, founded the Egyptian Museum in Cairo. Frederic Sauvage pioneered the ship's propeller. Sainte-Beuve, born 1804, became one of the founders of modern French literary criticism. More recently the town has produced the footballers Franck Ribery, N'Golo Kante and Randal Kolo Muani; the painter Georges Mathieu; and the organist Olivier Latry, who plays at Notre-Dame de Paris. A small city, oddly central to several stories.

By tonnage landed, no French port catches more fish than Boulogne. The trawlers come back in the small hours and the auction halls at the Capecure complex move some 30,000 tonnes of seafood a year through the wholesale market - tonnage that has fallen by nearly three-quarters since the 1960s but still leads France. The tidal range here is the biggest in the region: an average of eight metres between high and low water in the Pas de Calais, where the funnel of the English Channel narrows to its tightest pinch. Herring built the modern industry in the nineteenth century, when a handful of shipowning families - Vidor, Huret-Dupuis, Ancel-Joly - dominated the drifter fleet. Today the boats land mackerel, cod, sole, squid and scallops. Above the docks looms Nausicaa, France's national sea-life centre and one of Europe's largest aquariums.

Boulogne's whole history is bound up in the thirty-four kilometres between its cliffs and Dover's. The Romans launched their British invasion from here. The Vikings came up the Liane in the ninth century. Henry VIII besieged the town in 1544. Napoleon massed his Armee de l'Angleterre on the bluffs above the port in 1804, planning a crossing that never happened. The 20th Guards Brigade held the harbour for three days in May 1940 to buy time for Dunkirk. The Canadians retook the city in September 1944. Cross-Channel ferries ran until 2010, and as of 2024 a new freight-passenger line has begun to revive that link. The fishing boats still steam out before dawn. The cliffs across the water are still visible from the ramparts. Somewhere in between, a country watches another country and listens for its own echo.