Monstrum, a Danish firm creates some of the most unique playgrounds you’ll see. I like their take on design below:

MONSTRUM believes that playground design should be a reflection of the world surrounding us. 
We see the world as a place full of colour. We meet boys that like pink and girls that likes trees, so why only play on a monkey frame and a sandbox, when you can play in a moon crater or a submarine or a giant spider or an enormous snail or a Trojans horse or a rocket or an ant or a princess castle. The fantasy is infinite. 
The visual effect can endulge from a far, a tall slide, a massive tower or a wave to play on can draw kids in from the street. 
As artists and designers and through our experience with building theatrical set-design at numerous theaters in Copenhagen, we have the knowledge to combine elements where not only physical activities and play evolve, but also with a visual story that creates a space where fantacy thrives.

(via super punch)