A long bus tour of the city on changeover day(end of Transatlantic portion and beginning of Baltic cruise). We saw a great deal of the city, The Little Mermaid, the Queen's yacht, lots of public spaces, but the greatest kick-Tivoli Gardens. Marvelous site, allow time to tour it even though the cruise line doesn't offer it. Could have spent 3 or 4 hours there.
Didn't take the Berlin option (too long a train ride for us) but folks who did said they loved it. We took the the "Chugging on the Molli Steam Train" tour. Bus ride to Bad Doberan, cathedrals, then short train ride to beachside resort. Fun day, very different.
Didn't use ships tour for this one, took a local hop on hop off bus. Careful of the bus schedule, as in the early season they only stop at each location once an hour. Great medieval city, fantastic lunch at Olde Hanse restaurant. No electricity, candles everywhere, medieval style cooking, soup and salad to die for. Interesting place to just walk around in. Be sure to walk the narrow steps and street down from the tall tower to town square.