According to this article: http://adventureplaygrounds.hampshire.edu/history.html there are currently only two "adventure playgrounds" in the U.S.C. Th. Sørensen, a Danish landscape architect, noticed that children preferred to play everywhere but in the playgrounds that he built. In 1931, he imagined "A junk playground in which children could create and shape, dream and imagine a reality...His initial ideas started the adventure playground movement.
The first adventure playground opened in Emdrup, Denmark in 1943, during World War II. In 1946, Lady Allen of Hurtwood visited Emdrup from England and was impressed with "junk playgrounds." She brought the idea to London. These "junk playgrounds" became known as "adventure playgrounds."
The first three pictures are of the park named "Adventure Playground" in Huntington Beach, California mentioned in the article above, but most of the pictures appear to be just "playgrounds." If you removed the swings, slides, and other equipments, they would be parks.