Altena sits in a part of North Rhine-Westphalia rich in industrial heritage and medieval history, and the towns nearby reward a day's exploration.
Hagen (35 minutes by S-Bahn) is the largest city nearby and home to the Freilichtmuseum Hagen, an outstanding open-air museum of pre-industrial crafts and trades with reconstructed workshops and working demonstrations — a natural companion to the wire museum in Altena. Hagen also has a good art museum with a strong collection of early 20th-century German art.
Iserlohn (20 minutes west) has the remarkable Dechenhöhle, a large show cave in the limestone hills, and the remains of a fine Romanesque church. It is the nearest town of comparable size to Altena.
Lüdenscheid (20 minutes south) is the capital of the Märkisches Sauerland and has better shopping and a local history museum covering the region's plastics and metalworking industries.
Hohenlimburg Castle near Hagen is another well-preserved hilltop castle with a cutlery museum, worth combining with a trip to Hagen.
The Sauerland Höhenflug long-distance trail passes through the area, and the forested hills between these towns are connected by a network of marked paths suitable for half-day or full-day walks.