The Riss is a small river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in Baden-Württemberg

Baden-Württemberg

Baden-Württemberg is one of the 16 states of Germany. Baden-Württemberg is in the southwestern part of the country to the east of the Upper Rhine, and is the third largest in both area and population of Germany's sixteen states, with an area of and 10.7 million inhabitants...

, south-western 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...

, right tributary of 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....

. Its source is in Upper Swabia

Swabia

Swabia is a cultural, historic and linguistic region in southwestern Germany.-Geography:Like many cultural regions of Europe, Swabia's borders are not clearly defined...

, between Bad Waldsee

Bad Waldsee

Bad Waldsee is a town in Upper Swabia in Baden-Württemberg, Germany. It is part of the district of Ravensburg, in Oberschwaben. It is situated 20 km south of Biberach an der Riß, and 20 km northeast of Ravensburg. The town is known for its historic old city with many landmarks and large...

 and Bad Schussenried

Bad Schussenried

Bad Schussenried is a town in Upper Swabia in the district of Biberach, Baden-Württemberg, Germany.It lies on the Upper Swabian Baroque Route.Schussenried Abbey, a former monastery founded in 1183, is located in Bad Schussenried...

. It flows north, through the town of Biberach an der Riss. It then flows into the Danube between Ehingen

Ehingen

Ehingen is a town in the Alb-Donau district in Baden-Württemberg, Germany, situated on the left bank of the Danube, approx. 25 km southwest of Ulm and 67 km southeast of Stuttgart.-Statistics:...

 and Erbach

Erbach

-Places:*Erbach, a constituent community of Bad Camberg in Hesse*Erbach an der Donau, town in Baden-Württemberg**Erbach Castle, castle in Erbach an der Donau*Erbach im Odenwald, town in Hesse**Erbacher Schloss, castle in Erbach im Odenwald...

, approximately 20 km upstream from Ulm

Ulm

Ulm is a city in the federal German state of Baden-Württemberg, situated on the River Danube. The city, whose population is estimated at 120,000 , forms an urban district of its own and is the administrative seat of the Alb-Donau district. Ulm, founded around 850, is rich in history and...

. Its total length is approximately 50 km.

The Riss gave its name to the Riss glaciation, an ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

.