I was surprised to find fitness parks in Buenos Aires. There is one near me in Orlando, Florida. They are great and there is one not very far from our condo. I would love to see them in every city throughout our nation.
There are some fitness "stations" on a mountain trail where I used to run. However, being in an organized fitness park sounds like more fun and also safer. I'd definitely use one if there was ever one built up here in the rural area where I live. In fact, I might put a "letter to the editor" in our local paper and see if I can spread the idea.
I have never used a fitness park, simply because I have never seen one much less had access to one. (I like the idea though.)
However, I have used fitness trails where there are different fitness stations placed at intervals along the way -- like parallel bars, balance beams, chin-up bars, step ups, etc. You run, walk, jog to each 'quickie workout'.