Stockholm itself is made up of a number of islands, with mainland to the north and south, the Baltic to the east and lake Malaren to the west. There is an archipelago constisting of some 26000 islands of various sizes stretching out into the sea toward Finland.
A trip on the Waxholmsbolaget boat up to the small town of Vaxholm, 45 minutes away, is one of the best ways to understand the city. You get to see some of the pivotal sights and understand how the city is both divided and held together by the water.
The boat itself is a fairly small foot passenger ferry, although it does have a cafe, and the journey a little confusing if you’re not acquainted with the Swedish way of doing things – you board the boat and once on buy a ticket any time during your journey to your destination, as long as you have a ticket they will let you off again.
Return boats don’t run very frequently, so make sure you don’t miss the one you intend to catch, Vaxholm, while a pleasant little town, *is* a little town and cannot provide much in the way of entertainments for a four hour stretch between boats. There are plenty of cafes and restaurants overlooking the harbour, though, so if you’re worried you can just take a coffee in one of those and watch out for the boat.