Imagination is like any other skill. For some people it is easier than for others, but for all of us, it gets better with practice. 
A playground offers just as much opportunity for exercising the imagination as it does for exercising the body. The monkey bars can be a deep, dark jungle or an exciting circus or a space capsule. The swing can be a waterfall or a high mountain. The fort may be a pirate boat lurking on the ocean or a base station on another planet. Children sometimes need adult help to expand their imaginations beyond what they have recently seen on TV, movies or video. Kids also like to try various roles for themselves, monsters, princesses, animals, heroes, warriors, etc.
In addition to imagining various places and different roles, the imagination can also dream up new ways to play with the equipment. The ground often becomes the swamp or the burning hot lava and the trick becomes how to move on the equipment without getting a foot on the ground.
Sometimes, we have to imagine that the weather is better than it is, which may be the hardest task of all!
How do you exercise your imagination on the playground?