The metropolis can be understood as a complex adaptive system made up of complex adaptive subsystems that agglomerated to help create the city’s strength, resilience and dynamism. In particular, the accumulated strength and dynamism of the individual neighbourhoods that form and evolve its districts and the districts that form its regions have major impacts on the organisation and evolution of the metropolis. This article discusses the subsystems of the city, in particular its regional, district and neighbourhood transaction places or activity centres. While all metropolitan areas are complex adaptive systems, many urban subsystems constructed in the post–World War II period are not. They are instead chaotic or controlled by mechanical order. It will be argued that only the traditional ‘commons’ has the principles required of complex adaptive systems and that being such confers many benefits to the communities they serve.