For sure one of the nicest places in Stockholm for a coffeebreak - or "fika" as it is called in Sweden. In my opinion at least. Rosendal's trädgård is a not-so-hidden-anymore gem on the island of Djurgården. It is a garden where many flowers and plants grow outside or in greenhouses. The harvest is sold or they make delicious food out of it that can be eaten there. You buy your food in a greenhouse where they have meals for lunch but also many sweet things and such delicious food as open hummus-sandwiches. Then, you can sit in the beautiful garden surrounded by plants and trees. Or buy a coffee and a kanelbulle and sit in the park. You can also visit the greenhouses of course, buy plants, accessories and don't forget to visit the shop! There is also Rosendal's slott that can be visited.
To make it a roundtrip, take the tramway to Bellmansro, follow the signs and walk through the forrest. On the way back, leave on the other side of the garden and walk along Rosendalsterrassen, Sirihovswägen and Rosendalsvägen and then along the water back to Djurgårdsbron.
Find all the information about the openingtimes and more at the official website of Rosendal's trädgård.