Complex sentence: Boulogne-sur-Mer (Latin: "Gesoriacum" or "Bononia",), commonly known as Boulogne, is a city in Northern France and a sub-prefecture of the department of Pas-de-Calais.
Split into simpler sentences: 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.