In 1880, the steelworks of Port Sec and Prieuré united to form the Société des Aciéries de Longwy. The Maison de la Formation boasts a bona fide Art Déco treasure: the magnificent stained glass windows conceived by French decorator and furniture designer Louis Majorelle. The windows, which were incorporated right from the beginning of the building project in 1928, show steelworkers exercising different skills.