Willkommen in Deutschland!
Welcome to Germany!
For cruisers who do not like to go far away and "cheap", you can go to Rostock.
Rostock is the town of your pier in Warnemünde. Warnemünde is directly at the seaside while Rostock is connected through the river Warnow with the sea. Warnemünde means mouth of the river Warnow.
Next to the cruise terminal you can go by boat to Rostock and this gives you a chance to make great pictures of your ship:
So it's just three minutes walking from your cruise terminal to get on the boat to Rostock.
You can also take the train. It's a commuter train which go every 10-30 minutes (depending to weekday and time of travel). Transit time about 20 minutes plus walk to city 20 minutes or tram in five minutes.
Well: this is my personal opinion: looks like most other Hanseatic towns during a Baltic Sea Cruise...
One interesting thing to see:
On the left side it's true historical building.
On the right side: it's faked!!! It's a building made with precast concrete slabs, i.e. typical Communist construction style!!!
And here is a nice leaflet with all essential information you need to prepare your DIY-visit in Rostock: