The Hegau is a formerly volcanic landscape in southern Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 extending around the industrial city of Singen

Singen

Singen is an industrial city in the very south of Baden-Württemberg in southern Germany and just north of the German-Swiss border.-Location:...

 (Hohentwiel), between Lake Constance

Lake Constance

Lake Constance is a lake on the Rhine at the northern foot of the Alps, and consists of three bodies of water: the Obersee , the Untersee , and a connecting stretch of the Rhine, called the Seerhein.The lake is situated in Germany, Switzerland and Austria near the Alps...

 in the east, the Rhine River in the south, the Danube

Danube

The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....

 River in the north and the Randen—as the southwestern mountains of the Swabian Alb

Swabian Alb

The Swabian Alps or Swabian Jura is a low mountain range in Baden-Württemberg, Germany, extending 220 km from southwest to northeast and 40 to 70 km in width. It is named after the region of Swabia....

 are called—in the west.

The most famous sight of the Hegau is the Hohentwiel

Hohentwiel

Hohentwiel is an extinct volcano in the Hegau region of Baden-Württemberg in southern Germany. About 20 miles from Lake Constance, it lies in the German city of Singen....

, a volcanic stub. On top of the mountain lies Hohentwiel fortress. The castle that once stood there was destroyed by French troops during the Napoleonic Wars.

The Hohentwiel is the southernmost of a row of volcanic stubs in the Hegau, including the Hohenkrähen, the Hohenstoffeln, and the Hohenhewen.