Cities generate challenges as well as confer advantages on their inhabitants. Recent excavations and surveys in northern Mesopotamia have revealed extensive settlements with diverse populations, institutions, extended hinterlands, and mass production by the early fourth millennium BC, comparable to well-known evidence for cities in their traditional homeland of southern Iraq. However, early northern Mesopotamian cities incorporated low-density zones and flexible uses of space not yet identified in southern Mesopotamia. Evidence for violent conflict in northern Mesopotamian cities also raises questions about urban sustainability; cities succeeded despite new sources of social stress.