Chang'an was the capital of the Tang dynasty, and many other cities throughout East Asia were built to essentially the same plan: the palace/fortress is in the middle on a north-south axis, its location chosen precisely by geomancers to ensure the most auspicious setting (what is now commonly known as feng shui) and successive rings of walls surround it. The closer you are to the throne room in the dead centre of the palace, the more important you are.