The chapter examines the changing urban landscape of the western Roman Empire and its successor states from approximately 300 to 600. It explores how cities evolved in response to shifting political, economic and social conditions, analysing archaeological evidence and urban-planning trends. The chapter begins with an overview of recent developments in the field and outlines the diverse trajectories of urban centres across the region. Of central importance is the gradual transition from classical urbanism to post-classical forms, marked by the loss and reuse of monumental structures, the fortification of cities and the adaptation of existing infrastructure. Rather than depicting urban change as a straightforward decline, the chapter argues that cities underwent complex transformations, with some centres experiencing contraction while others remained vibrant. It also illustrates how elite participation, religious shifts and administrative restructuring influenced the built environment. Furthermore, attention is given to the role of city walls, which were expanded or reinforced to accommodate new defensive needs. The reuse of materials, including spolia, became a defining feature of late antique architecture. By integrating textual and material evidence, the chapter provides a nuanced perspective on how cities adapted to the challenges of Late Antiquity, maintaining their significance despite profound structural changes.