The epic Nordiska Museet is Sweden’s largest cultural-history museum and one of its largest indoor spaces. The building itself (from 1907) is an eclectic, Renaissance-style castle designed by Isak Gustav Clason, who also drew up Östermalms Saluhall; you'll notice a resemblance. Inside is a sprawling collection of all things Swedish, from sacred Sami objects to clothing and table settings. The museum boasts the world’s largest collection of paintings by August Strindberg, as well as a number of his personal possessions.
In all, there are over 1.5 million items in the museum's collection, dating from 1520 to the present day. Topping it off are the often dynamic temporary exhibitions. The insightful audio guide (free with admission) offers several hours of English commentary.