On topic of museums: Stockholm definately has the greatest ones! There is Armemuseum, that has warfare starting from stone age to modern day, but in a very compact style that you can easily walk thru it. Some very clever stuff too, like a diorama of a 30-years war era army in miniatures and listed how much of food and supply it used every day. I remember they needed crazy amount of beer! Also you can measure different era guns in your hand and target "enemy" with it, in a way that you see how close the targets were in battles of their eras. (Early musket, brown bess, rifle..) The royal armory museum near King's castle has lots of great things, like the clothes king Gustavus Adolphus had on when he was killed, his horse, the clothes Carolus Rex had on when he died too etc. Vasa ship museum, the most popular museum of Nordic countries, you see there a 1600-century ship that was salvaged from the deep and restored, very interesting atmosphere.