Really? I never see kids playing outside at the park. It's fair game as far as I am concerned.
However, many conditioning drills I like to do do not require a playground -- any old strip of dirt, grass, or parking lot is all that is required. I like to do sprints, running and mobility drills, bear crawls, burpees, jumping. These are all great conditioning movements that can be combined in various ways to keep one fresh and motivated.
A few examples might look like these:
Sprint 100 meters, do 50 jumping jacks, bear crawl back to start, 50 push up, repeat for given number of rounds or time.
25 walking lunges, shuffle back to start, 17 tuck jumps, wash, rinse, repeat.
We are only limited by our imaginations. A few cheap pieces of equipment added into the mix can even make for more variety: e.g., sandbags, jump rope, medicine ball, etc. The key to conditioning is that variety does matter.