Lens (läNs) [key], city (1990 pop. 35,278), Pas-de-Calais dept., N France. During the 19th and 20th cent. it was one of the most important coal centers in N France, but its mines are now closed. Much of the city's manufacturing has been replaced by service-oriented industries. The victory there (1648) of the French under Louis II de Condé was the last important battle of the Thirty Years War. Lens was occupied and devastated by the Germans in both world wars. A branch of the Louvre museum opened here in 2012.