Yes, it is announced everywhere as the number one attraction in Stockholm: The Vasa museum! But is it really worth to go see a ship that sank in the harbour of Stockholm in 1628 on its maiden voyage after only 1300 meters of sailing? My opinion: Definitely! And here is why:
The Vasa museum is built on the island of Djurgården and you easily find it because you can see the vessel's mast on top of the museum already from far away. On a rainy day, take the tramway, leave at Nordiska museet/Vasa museet and walk for a few minutes. If you pay with creditcard, you'll be inside very fast. Then you see the ship. Your reaction might be "All that fuss about this small thing?". That was at least mine. But then, before starting the tour, make sure you pick up a brochure where it's described that for example you can use the free Wifi to get a MP3-tour. Which is a briliant idea, because it is basically a free audioguide in your language and on every interesting point you get the story behind it on your smartphone.
Then start with watching the movie about the construction, sinking and the salvage in 1961, which is very interesting. It is showed in many different languages, check out the website for the exact times. And then you can start to discover the Vasa on seven floors. When passing it by for the first time, you will realize that it is everything else than small. It actually is huge! And all wooden and in a great shape that doesn't make you believe that it's been on the ground of the sea for decades. On the different floors, there are many exhibitions and you can learn more about the story of the Vasa, the construction, the people, the sinking. And you can see the Vasa from many different views. Take the time to visit all the floors, there's always something new to discover on this ship. Especially the very detailed wooden sculptures everywhere along the ship are impressive.
There's something for the entire family in the museum and you don't necessarily have to be interested in ships when visiting the museum. Check out the opening hours before your visit. Entrance fee is 150 SEK for adults, childres and adolescents until the age of 18 are free of charge.
Have fun discovering the mighty Vasa!