(clara vallis), a town in the northern province of Oesling, grand-duchy of Luxemburg, on the Clerf, a tributary of the Sure. Pop. (1905) 866. In old days it was the fief of the de Lannon family, and the present proprietor is the bearer of a name not less well known in Belgian history, the count de Berlaymont. The old castle of the de Lannoys exists, and might easily be restored, but its condition is now neglected and dilapidated. In 1798 the people of Clervaux specially distinguished themselves against the French in an attempt to resist the institution of the conscription. The survivors of what was called the Kloppel-krieg (the "cudgel war") were shot, and a fine monument commemorates the heroism of the men of Clervaux.