Rainbow is modeled on the concept of public adventure playgrounds—or “junk playgrounds,” as they were initially called—which originated in Denmark. The first adventure playground was built in Emdrup in 1943, in the midst of the German occupation of Denmark during World War II. The prominent landscape architect Carl Theodor Sørensen is usually credited with having come up with the idea after noticing that children liked playing with leftover building materials at construction sites.
