Signal Iduna Park — built in 1974 and still known to locals as the Westfalenstadion — is one of Europe's most celebrated football grounds. With a capacity of over 81,000 for domestic matches, it is Germany's largest stadium and ranked consistently among the most atmospheric venues on the continent. The ground sits in the Westfalenpark, south of the city centre, and can be reached directly by U-Bahn on match days.
Guided stadium tours run on non-match days and take in the dressing rooms, the press box, and the pitch-side tunnel. The attached fan shop is one of the largest club merchandise stores in Germany. Even if football leaves you cold, the scale of the place — and the fanaticism it has inspired — is worth an hour of your time.