The region of southern Mesopotamia, in modern southern Iraq, was home to perhaps the world's oldest cities and complex societies. Such cities and towns developed closely to irrigation works and other water features, with major settlements developed along levees and so-called turtle backs made up of natural accumulation and human-made debris. While water was a critical component to the rise of cities, it was also the unique evolution of societies to their complex landscape, including the development of different social practices that made the region develop early cities. By-products of these social developments included religious institutions and inequality but also the rise of governments, written language, laws, and other forms of social development we associate with our own societies. Recent work in southern Iraq demonstrates that the region was likely occupied much earlier than we thought; new climate data and other work will mean our picture on how the environment shaped the development of urban-based societies in southern Mesopotamia will evolve in the coming years. New fieldwork, including surveys and excavations, will also shape a new understanding of how urbanism arose in this complex landscape.