My favourite park in Stockholm is Skinnarviksparken, somewhat hidden and strangely google maps doesn't show it as a park area.

Anyways, this place is the bee's knees, it has everything: a wonderful view, you can choose between sitting on stone or gras, coffee and great kanelbullar are not far, they actually live in a little kiosk at the park entrance. There's lots of barbecue in the evenings and you can see the sunset as well as the sunrise! Never at the same time though, unfortunately Stockholm is not quite that high up north.