The ferryboat tour from Stockholm is very scenic and entertaining. The route goes through the beautiful Turku archipelago which can be admired also late in the evening because the sun sets very late at this latitude. The boats are truly luxurious and offer all kinds of entertainment including many restaurants and excellent food.
There are two companies operating this route, Viking Line and Tallink-Silja. The travel time is roughly 10 h. The detailed timetables and prices of Viking Line and Tallink-Silja are found at the respective companies' sites. Both companies have two daily departures from Stockholm. If you choose the morning departure you can enjoy the scenic tour in daylight. Opting for the evening departure gives you the opportunity to test various entertainments on board and sleep in a luxurious cabin.