Sweden's parliament sits on Helgeandsholmen, a small island wedged between Gamla Stan and Norrmalm. The current building combines a Neoclassical facade from the 1900s with a modern glass-and-granite addition from the 1980s. Free guided tours run on weekends during the parliamentary recess (summer and some holidays), taking you through the debating chamber and the ornate former upper house.
The building's location is striking — surrounded by water on all sides, with views across to the Royal Palace. Even if you don't go inside, the island itself makes for a pleasant short detour between the old town and the city centre.