Junkyard/adventure playground inspiration
Designing playgrounds for happier, healthier kids

Science says kids learn more when we leave them alone. This 3 minutes long video demonstrates the benefits of free play and healthy risk taking.
Awareness of body and space, resilience, stretch of imagination through free play on junk playgrounds

Interaction between education and play from evolutionary perspective.
Reasons and consequences of decline of self-directed free play on child development