Aldo van Eyck built his first playground in Amsterdam. in 1947 It was a spatial experiment that marked the childhood of many kids.  His playgrounds were built in a time of need with the baby boom after the war. His playgrounds were part of a movement towards “bottom up architecture that literally aimed to give space to the imagination.” He designed hundreds of playgrounds between 1947 and 1978. Only 90 survived into the 21st century with their original layout.

source: https://merijnoudenampsen.org/2013/03/27/aldo-van-eyck-and-the-city-as-playground/