Take an overnight cruise to Finland, Estonia or Latvia from downtown Stockholm! It's a fun way to get around to the countries surrounding Sweden!
The cruise ships are huge, with tons of amenities: Nightclubs, saunas, restaurants, children's playrooms, concerts, and other entertainment. And don't forget the duty free shopping!
There are two large Cruise Lines to choose from, Silja Line and the Viking Line. Both have different advantages (and are usually priced around the same) so check both out to determine which might be a better fit for you!
The Silja port is approx 2o Minutes from Central Station with public transport, the Viking Line Terminal is about 15 mins away