This is a great spot for lunch or coffee! In the summer you can sit outside. They have a beautiful botanical garden and is located next to Brunnsviken (lake). The also have a huge greenhouse with plants from allover the world.
In the summer this is a haven in the middle of the city. It is a public garden where I like to go and relax in the grass under a blooming tree. There is also a cafe and a shop here. Before you leave you should buy a bouqee of flowers (you pick yourself in the garden!).