Some locals admit that Kiel, the capital of Schleswig-Holstein, has a city centre that's grottenhässlich (ugly as sin). And unfortunately it is true; it was obliterated during WWII by bombing raids on its U-boat pens and then rapidly rebuilt. Today, it is a series of charmless indoor malls linked by pedestrian bridges.
However, Kiel's grand harbour continues on as it has for centuries and this, along with the city's museums, should be the focus of your visit. Huge ferries transport millions of passengers to and from Scandinavia, while summer sees locals strolling the long waterfront promenade.