Contemporary cities are going through an uncertain period of transformation. The shift from spatial relationships characteristic of core-periphery models to more dispersed patterns typical of polycentric settlements is closely connected with socio-environmental dimensions. Horizontal settlement expansion carries negative consequences for agricultural land, forests, semi-natural environments, and wetlands. Urbanization-driven landscape fragmentation disrupts ecosystems and reduces ecological connectivity, increasing greenhouse gas emissions and exacerbating climate warming. In this framework, polycentrism emerges as a relevant approach to complement sustainable urban planning, focusing on the creation of interconnected nodes capable of fostering economic agglomerations and regional synergies. Cities are seen as self-organized complex systems evolving in response to external and accidental stimuli. Metropolitan transformations become unsustainable when they show adverse effects, requiring integrated approaches that combine environmental sustainability and regional development.