The Lenne is a river in the Sauerland

Sauerland

The Sauerland is a rural, hilly area spreading across most of the south-eastern part of North Rhine-Westphalia, in parts heavily forested and, apart from the major valleys, sparsely inhabited...

 area in North Rhine-Westphalia

North Rhine-Westphalia

North Rhine-Westphalia is the most populous state of Germany, with four of the country's ten largest cities. The state was formed in 1946 as a merger of the northern Rhineland and Westphalia, both formerly part of Prussia. Its capital is Düsseldorf. The state is currently run by a coalition of the...

, 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...

, a left tributary of the Ruhr.

Having its source on top of the Kahler Asten

Kahler Asten

The Kahler Asten is an 841.9-meter-high mountain in the Rothaargebirge range in the district of Hochsauerland, in the German state of North Rhine-Westphalia...

near Winterberg

Winterberg

Winterberg is a town in the Hochsauerland district of North Rhine-Westphalia, Germany and a major winter sport resort of the Wintersport Arena Sauerland.-Geography:...

 in an intermittent spring at an elevation of 2,687 feet, the Lenne ends after a course of 128 km flowing into the Ruhr river near the city of Hagen

Hagen

Hagen is the 39th-largest city in Germany, located in the federal state of North Rhine-Westphalia. It is located on the eastern edge of the Ruhr area, 15 km south of Dortmund, where the rivers Lenne, Volme and Ennepe meet the river Ruhr...

. With an average discharge of 25 m³/s near its mouth, it is the main tributary of the Ruhr. Both rivers are quite close to each other at their sources, but spread to different routes until they meet again in Hagen

Hagen

Hagen is the 39th-largest city in Germany, located in the federal state of North Rhine-Westphalia. It is located on the eastern edge of the Ruhr area, 15 km south of Dortmund, where the rivers Lenne, Volme and Ennepe meet the river Ruhr...

. Towns along the Lenne are Schmallenberg

Schmallenberg

Schmallenberg is a town in the district of Hochsauerland. Relating to its area of 188 square miles it is the largest town belonging to an administrative Kreis in the federal state of North Rhine/Westphalia, Germany....

, Lennestadt

Lennestadt

Lennestadt lies in the Sauerland in southeast North Rhine-Westphalia and is a community in Olpe district. It is the district’s most populous municipality....

, Finnentrop

Finnentrop

Finnentrop is a community in Olpe district in North Rhine-Westphalia, Germany.- Geography :Finnentrop lies near the forks of the rivers Bigge and Lenne in the Sauerland and is divided into the following constituent communities:- History :...

, Werdohl

Werdohl

Werdohl is a town in the district Märkischer Kreis, in North Rhine-Westphalia, Germany.-Geography:Werdohl is located in the hills of the Sauerland, at a double meander of the river Lenne and its confluent, the Verse...

, Altena

Altena

Altena is a town in the district of Märkischer Kreis, North Rhine-Westphalia, Germany. The town's castle is the origin for the later Dukes of Berg. Altena is situated on the Lenne river valley, in the northern streches of the Sauerland.-History:...

, Iserlohn

Iserlohn

Iserlohn is a city in the Märkischer Kreis district, in North Rhine-Westphalia, Germany. It is the largest city by population and area within the district and the Sauerland region.-Geography:...

, and Hagen. The lower part of the Lenne valley is characterized by great altitude differences to the surrounding plateaus and by a concentration of small-scale industry along the river.