Altena is a town located in the district of Märkischer Kreis within the state of North Rhine-Westphalia, Germany. It is situated in the northern reaches of the Sauerland region, specifically positioned along the Lenne river valley.
The town is historically significant as the site of Altena Castle, which served as the origin for the later Dukes of Berg. This historical landmark remains a primary point of interest regarding the area's heritage.