The concept of a defensive measure put in place to protect urban centers is not new to China. Neolithic settlements such as Banpo utilized deep ditches, possibly to deter wild animals and trespassers. Such defense projects grew exponentially with economic development. Initial construction of what was to become the Chang’an city wall began in 194 B.C. during the Han dynasty. The original wall stretched for 25 kilometers with a thickness of 12-16 meters. It was rebuilt on numerous occasions and the story of its current incarnation begins in the Ming dynasty (1368-1644). Newly appointed emperor Zhu Yuanzhang initiated a movement to fortify Chine’s cities, including the recently named ‘prefecture of Xi’an.’ In 1370 construction of one of the oldest and best preserved city walls in China began. The rectangular structure, almost fourteen kilometers long, twelve meters high and fifteen meters wide developed into one of the largest ancient urban military defense systems in the world.
Original walls were typically constructed from compressed earth, lime and glutinous rice extract, and in 1568, a government officer Zhang Zhi had the wall rebuilt with bricks. The new structure contained a total of 98 defensive ramparts and sentry buildings. The city could only be entered through one of the four gates, each comprising of three towers, the Zhenglou, Jianlou and Zhalou. The Zhalou stands apart from the city wall opposite the Zhenglou and it was used to raise and lower a draw bridge. Further out is the Jianlou (or Arrow Tower) which functioned as a defensive outpost. The Jialou and Zhenglou towers were connected by a tunnel, where soldiers would be stationed. A watch tower was positioned on each of the wall’s four corners. Today’s wall is still regarded as a central landmark dividing the city into inner and outer districts.