Martin Luther King, Jr. Park is a great park, and very heavily used. You can see dog walkers, soccer players, softball players, tennis players, families have a picnic, pick-up ball on the court, and much more. Down in this little corner of the park, there is generally less activity, and a mysterious, disused box. There is no need to open that box in the course of your search.
First to find credit goes to Holy Strollers!