The essays presented in this volume describe a phenomenon so widespread in human time and space that its importance is easily overlooked. City walls shaped the history of warfare; the mobilization of manpower and resources needed to build them favored some kinds of polities over others; and their massive strength, appropriately ornamented, created a visual language of authority. Chapters by historians and art historians explore how separate traditions throughout the world illustrate universal themes of defensive strategy and the symbolism of power, each time embedded in a distinctive local context.