As cities and towns are created and maintained over time, structures are built and re-built to facilitate the functions of these settlements for human purposes.  These structures include buildings used for dwellings, factories, shops, recreation, education, social and other purposes.   Buildings provide a wide range of benefits for cities and towns by facilitating many of their key activities.   

However, the ways that built structures and the uses to which they are put are arranged spatially over a human settlement, the connections between these, and the materials and design qualities of the structures themselves all have implications for the sustainability of cities and towns.  

In particular, as we seek to reduce carbon and other emissions, as fossil fuels decline, and we seek to recognise the implications and impacts of built environments upon ecological systems, new ways of designing, creating, reusing, maintaining and envisaging built structures are needed if cities and towns are to be sustainable.  In parallel, we need new ways of including and interacting with the functions of the natural world as we increasingly understand the necessity of maintaining ecological systems to ensure the sustainability of built environments.  The nature of built structures has a range of implications for the resilience of cities against disasters, such as floods, cyclones, bushfires and earthquake.  Further, the ability to adapt cities to meet climate change challenges is impacted upon by the nature of the built structures themselves.