 Instead, the city's administrative center was spread over a relatively large area, which may or may not have been surrounded by a second set of "inner" walls similar in shape and construction to the main outer wall.Long-term strategic considerations meant that the walls of important cities often enclosed an area much larger than existing urban areas in order to ensure excess capacity for growth, and to secure resources such as timber and farmland in times of war.The city wall of Quanzhou in Fujian still contained one quarter vacant land by 1945.