If you’ve already savored the beer, brats, and big cities of Germany, it may be time to escape the crowds and dig deeper by visiting this European country’s smaller heritage cities.   At the invitation of Historic Highlights of Germany, I recently explored four northern German cities that are rich in history. Rostock, Lübeck, Osnabrück, and Münster are part of the Germany’s Historic Highlights program that introduces seasoned travelers to the country’s smaller heritage cities.   These cities also offer more than a trip back...