You can also go to Tivoli, or an amusement park called Grona Lund. It's really hilarious and you have a lot of attractions.
Also, if you're in Stockholm, you can also see the Vasa Museum, which is a big ship which the King Vala had, which is really interesting.
But if you want to go outside Stockholm, you should take a road trip from Stockholm to another big town called Gothamberg which is in the West Coast.
During the summer it's really beautiful, and the whole Sweden is green by all the trees, so you should definitely take a road trip from Stockholm to Gothamberg.
If you're in Sweden during the winter you should go up north to the ice hotel. Everything is ice. The beds, the rooms, the doors, the whole ground is made my ice. And you can drink a lot of good drinks in ice. Well, cups made of ice. That's a good experience to do.