Graz is pretty well served for playgrounds - there's even a map which lists them all, but this one is very good. it has swings, slides, climbing frames, a sand pit and a water feature, by which I mean, a water feature that the kids are meant to play with! They can pump the water from the top of the...
Maybe the best place to have relax and a quick take-away lunch visiting the city in a day. I suggest to get at the top of Schlossberg by this side walking on the Weldenstrasse (the hornbeams way): in late october is something magic!
I liked this garden and its trees, flowers, fountain and grass and it was calm 2 hrs which I spent there but I saw many strange people who were exchanging something (I think drugs). Otherwise everything thins is nice.