Bouches-du-Rhône is a department in the south of France named after the mouth of the Rhône River. It is the most populous department of the Provence-Alpes-Côte d'Azur region. The principal mountains of the department are the Sainte-Baume massif (1 042 metres), Mont Sainte-Victoire (1 011 metres), the Garlaban massif and Alpilles massif. The largest city in the department, Marseille, contains a major industrial harbour and serves as France's largest commercial port.