The narrowest street in Sweden looks very romantic and worthy of a picture or two. Don't come out of your way to visit it, but if you're within proximity, this is surely something you should see.
The alley has an interesting, historical charm and although you won't be able to hold someone's hand while strolling through, the ambience of this place will make up for it.
It's relatively close to other attractions, but you can also get here by bus - station Kornhamnstorg, lines 57 and 59.
Wikipedia https://en.wikipedia.org/wiki/Mårten_Trotzigs_Gränd
Address 1 Mårten Trotzigs gränd, Stockholm 11129, Sweden
Coordinates 59°19'23" N 18°4'22.05" E