The Fossa Eugeniana or Spanish Rhine-Maas canal was a large-scale ambitious project of the Thirty Years' War

Thirty Years' War

The Thirty Years' War was fought primarily in what is now Germany, and at various points involved most countries in Europe. It was one of the most destructive conflicts in European history....

  planned by the then Spanish regent in Brussels, Isabella Clara Eugenia

Infanta Isabella Clara Eugenia of Spain

Isabella Clara Eugenia of Austria was sovereign of the Spanish Netherlands in the Low Countries and the north of modern France, together with her husband Albert. In some sources, she is referred to as Clara Isabella Eugenia...

, after whom it was named, during the years 1625-1629. It consisted of a fortified canal intended to blockade by river the United provinces, in order to divert trade from the Rhine just south of Wesel

Wesel

Wesel is a city in North Rhine-Westphalia, Germany. It is the capital of the Wesel district.-Division of the town:Suburbs of Wesel include Lackhausen, Obrighoven, Ginderich, Feldmark,Fusternberg, Büderich, Flüren and Blumenkamp.-History:...

 and reroute it to Venlo

Venlo

Venlo is a municipality and a city in the southeastern Netherlands, next to the German border. It is situated in the province of Limburg.In 2001, the municipalities of Belfeld and Tegelen were merged into the municipality of Venlo. Tegelen was originally part of the Duchy of Jülich centuries ago,...

 on the Maas, in Spanish territory.It was also known as the Spanish Rhine-Maas canal, when at the time spanish garrisons in north-western Germany reached its maxium extening, amounting to around fifty fortresses and forts. It was 4.30 meters wide and 60 km long.