The paper argues that physical environments are relevant and at time critical elements of the cognitive activities of individual agents and communities, and this should become an important consideration in designing such environments. To this end, the concept of stigmergy can be instrumental to the evaluation and design of environments that facilitate cognitive and information processing activities of human individuals and communities. Stigmergy is here introduced both as an explanatory principle and as the operative mechanism by which structured environments can operate as mediums of shared knowledge and mediators of self-organizing processes of coordination among loosely coupled individuals. The arguments are supported by three case studi...