When walking around in Gamla stan, taking a look at the doors is definitely worth it. There are some really beautiful ones around. Especially in the less frequented streets. There are many reasons to leave Västerlånggatan anyway, so walk some of the colourful small streets and discover some special doors. Remember that some of the houses in the old town are a few hundred years old. Also have a look on what you can see above the doors, there are old flags or sculptures or plates.
Find out what else can be done and seen in Gamla stan and in all other parts of Stockholm.