The two crossword solutions for the term 'River in Belgium' are YSER and SENNE. The Yser is a river in the Belgian province of West Flanders, and is a tributary of the North Sea. It is known for its role in World War I, when it was used as a defensive line by the Belgian army against German forces. The Senne is a river that runs through Brussels, the capital of Belgium. It is a tributary of the Scheldt, and is an important source of drinking water for the city.