Stockholm is a lovely city all year around, with its many islands and parks - but mid winter and mid summer are special.
For a special city vacation, come visit in late February or March, when there's often plenty of snow, sun, and beautiful views.
Boat tours are always nice, but sitting in a boat crunching through the ice as it is cruising between the 23.000 islands in the Stockholm archipelago is special. (See http://www.waxholmsbolaget.se for more info)
It's not all pretty snow covered views though.
I took these pictures last february. It was more or less snowing for three days, and quite a struggle to find cars in the morning.