Playgrounds were built with the intention to be climbed by the creative and adventurous minds of kids. Unfortunately, they are usually child-sized, but with a little creativity, you can turn them into an adult-sized training centre.
There are advantages of training here. One, they’re a public space (ignore the sign that says “Designed for kids under 12”). Two, they have a set of equipment that’s made for jumping and climbing. Three, they frequently have soft mulch or rubberized underfoot, so in the event that you screw up, you’ve got a safety cushion.
The drawback is kids. Beware that you don’t enrage their parents or, worse yet, trample the children. Avoid practising near children whenever possible.