Maybe I'm just lucky, but there is outdoor "gym" gear in plenty of places where I live, free to use for anyone. Including monkey bars and such.
As for specifically fitness as an activity, there is plenty of types of exercise that favor body weight exercises and free weights over machines. Crossfit is obviously the big trendy one, but there are many other types out there.
Nono, I'm talking about fun equipment, not gym style. Adult-compatible and -allowed ropeways (also without seats, you just hang on) and slides and seesaws and carousels.
The local indoor playground used to have an evening where they inflated the inflatable structures a bit more and only let adults in (so no crushed kids). You can power yourself out very fast like that, especially if you bring some friends. That's the feeling I want, not a gym.
