There's one near where I used to live in Chicago. They use a local Forest preserve. Strangely there is a contigent of neighbors who continually try to get the whole thing shutdown because they don't think young kids should be outside like that all the time. They try to complain and say they leave garbage or are noisy or other invented complaints. From what I understand, what they're really upset about is that they can't let their dogs run around off the leash with little kids around all the time.