Boulogne-sur-Mer (, Latin: Gesoriacum or Bononia, ) is a city in Northern France. It is a sub-prefecture of the department of Pas-de-Calais. Boulogne lies on the Côte d'Opale, a tourist coast on the English Channel, and is the most-visited location in its region after the Lille conurbation. Boulogne is its department's second-largest city after Calais, and the 59th largest in France. It is also the country's largest fishing port, specialising in herring.