Luxembourg has a number of minor rivers, such as the Eisch, the Alzette, and the Pétrusse, but the main river is the Moselle with its tributaries-the Sûre and the Our. Together, their courses serve as a natural boundary between Luxembourg and Germany. Along their banks, many of the country's medieval castles can be found.
Luxembourg is divided into districts, which are divided into cantons, which are divided communes. A dozen of the communes have city status, and one, Luxembourg City, is further divided into quarters.