Cities and towns have become the primary human living space. Since 2007, more than half of the world’s population has been living in urban areas and the figure is estimated to exceed 70 per cent by 2050. Building sustainable cities requires investment in (a) renewable energy sources, (b) efficiency in the use of water and electricity, (c) design and implementation of compact cities, (d) retrofitting of buildings and increase of green areas, (e) fast, reliable and affordable public transportation and (f) improved waste and recycling systems. Cities are diverse in terms of their size, structure, spatial form, economy, wealth, local resources availability and ecological impact (Sustainability in American Cities, Slavin 2011).