Even by German standards, INGOLSTADT , 60km due north of Munich, reeks of prosperity, courtesy of its four oil refineries, fed by pipelines from France and Italy, and the Audi car factory which migrated from Zwickau when the Iron Curtain went up. At least some of the wealth generated is used wisely, for the town spends more money on the upkeep of its historic monuments than anywhere else in Bavaria. For centuries one of Germany's most redoubtable fortresses, Ingolstadt is compact enough to be seen in a day, and has the benefit of being unspoiled by mass tourism.