The department is surrounded by the French departments of Marne, in the region of Lorraine by the department of Meuse, in the region of Picardy by the department of Aisne and by Belgium on the north, in the Region of Champagne-Ardennes.
Situated in the Ardennes uplands on the border with Belgium, the department of Ardennes includes many areas of very dense woodland. The principal river is the Meuse River.
The Ardennes is a region of extensive forests, rolling hills and old mountains formed on the Givetian (Devonian) Ardennes mountains, primarily in Belgium and Luxembourg, but stretching into France (lending its name to the Ardennes département and the Champagne-Ardenne région), and geologically into the Eifel. In Wallonia, the word 'Ardenne' in the singular is commonly used for the Belgian part of the region and in the plural for the French one. Ardenne is the origin of the great industrial period of Wallonia, the second of the world (18th, 19th and 20th centuries). In France, the word 'Ardennes' in the plural, together with the definite article, is commonly used to refer to the French Department of that name. Much of the Ardennes is covered in dense forests, with the old mountains averaging around 350-500 m (1,148-1,640 ft) in height but rising to over 650 m (2,132 ft) in the boggy moors of the Hautes Fagnes (Hohes Venn) region of north-eastern Belgium. The region is typified by steep-sided valleys carved by fast-flowing rivers, the most prominent of which is the Meuse. Its most populous cities are Verviers in Belgium and Charleville-Mézières in France, both exceeding 50,000 inhabitants. The Ardennes is otherwise relatively sparsely populated, with few of the cities exceeding 10,000 inhabitants with a few exceptions like Eupen or Bastogne.
The Eifel range in Germany adjoins the Ardennes and is part of the same geological formation, although they are conventionally regarded as being two distinct areas.
The highly strategic position of the Ardennes has made it a battleground for European powers for centuries. The region repeatedly changed hands during the early modern period, with parts or all of the Belgian Ardennes being incorporated into France, Germany, the Spanish Netherlands, the Austrian Netherlands and the United Kingdom of the Netherlands at various times. In the 20th century, the Ardennes was widely thought unsuitable for large-scale military operations due to its difficult terrain and narrow lines of communications. However, in both World War I and World War II, Germany successfully gambled on making a rapid passage through the Ardennes to attack a relatively lightly defended part of France. The Ardennes saw three major battles during the world wars – the Battle of the Ardennes in World War I, and the Battle of France and Battle of the Bulge in World War II. Many of the towns of the region were badly damaged during the two world wars.
