A lot of the stations that are used for public transport in Stockholm are works of art. So when you are in Stockholm follow the “T-“signs (which stands for “tunnelbana”, the subway) and luckily you will discover a well designed station.
Or even better, you can do an artwalk and chose the most interesting stations selectively. As for almost everything there is an app available for that. Unfortunately we didn’t have that app back in 2015 when we have visited Stockholm. But it’s a good impulse to re-visit this beautiful place.