The Ardennes are also known as the Ardennes Forest or Forest of Ardennes. Low hills with extensive forests and rough terrain, extending over Belgium, Luxembourg, France and Germany. Geologically, the range is a western extension of the Eifel in Germany. Raised during the Givetian age of the Devonian (382 to 387 Ma), the former mountain ridge is eroded to its basement. This is called the Hercynian orogeny, which created other mountain ridges in central Europe, e.g. the Armorican Massif, the Massif Central, and the Vosges. It shows metamorphic rocks, shists and marble, intensive folding and tectonic movements.