It’s taken a few decades, but Germany’s seventh-largest city has mastered the transition from industrial powerhouse to city of commerce and culture like few others. Van Gogh, anyone? Go to the Museum Folkwang. Fancy a look at Emperor Otto III’s gem-studded childhood crown? Head for the cathedral treasury. A Unesco-listed Bauhaus-style coal mine with a a fabulous museum? Look no further than Zollverein.