Impressive but small museum featuring mostly 20th century modern art. The current (Nov 2015) temporary exhibition "Reality Machines" by Olafur Eliasson is outstanding. The museum is located on Skeppsholmen Island very close to downtown Stockholm. Entry free with Stockholm card.
I have never been to such an incredible modern art museum EVER. I went here on an impromptu 'first date vacation' with my boyfriend. There was an awesome Duchamp and Picasso exhibit and tons of selections from other contemporary artists. The most striking exhibit was a collection of Hilma Af Klint's work. This Swedish woman is a pioneer of abstract art and depicts many philosophical, scientific, and religious themes throughout her paintings. 20 years after her death in the 40s her art was finally revealed to the public. Overall, this museum is absolutely one of the best I've ever visited. Worth it.
Good exhibits, garden, and restaurant. I enjoyed the Fantastic Paradise outside the museum very much. The sculptures by Niki de Saint Phalle and Jean Tinguely are fun to look at. The restaurant has good food and great view of Stockholm. Architecture museum is right next door.