Walled city is much more complicated than this.

If you study its building structure it is crazy! It is so "organic" that it is "growing" in every minute and surprisingly it didn't collapse! The walls are share with the others, the corridors are the remaining space when there is no space to build.

picture link: www.scmp.com/sites/default/files/2013/03/16/scm_news_1.1.nws_backart1_1_0.jpg