Green specializes in designing natural play spaces. They, "Enhance existing and natural features of a landscape to create exciting, interesting and beautiful spaces for learning, play and being together." The two huts above are just a couple of the structures they have designed to fit within the landscape. If you're looking for more information on natural play spaces their site is a great resource.
Most of the time when we design, we imagine a space fixed in time never ageing, but a natural play space evolves with the landscape. It changes with the seasons and matures with time.