If we hadn not been to Rome and Venice before Stockholm, we probably would have compared the Italian cities to Gammla Stan.
This is a small area of twisty streets that is an an absolute delight. There is very little in Stockholm that represents history except for Gammla Stan. In a cruel twist of fate, Stockholm decided to clear and destroy areas of its old buildings after WWII. Since Sweden was neutral during the war, it remained one of the few areas not damaged by bombing. So, they choose to destroy it themselves. The only place they did not affect was Gammla Stan. Thank goodness.
Other than the Vasa and the Opera house, this area is the one reason to visit Stockholm.