A port city on the north-east coast of France, on the English Channel. For a long time it was one of the places where ships from Dover in England arrived, carrying passengers and cars across the water. Calais is the more famous neighbour now, and the tunnel under the Channel has taken a lot of that traffic, but Boulogne is still a real fishing and ferry town. The full French name is Boulogne-sur-Mer (‘Boulogne on the sea’), which tells it apart from another Boulogne that is a suburb of Paris. Though actually, English often just says Boulogne when the Channel port is meant. It is a place name, so it takes a capital letter.