Xi’an Ancient City Wall is an extension of the prior Tang dynasty structure. It was built from the year of 1370 to 1378 and has a rectangular–shaped construction. It is over 4 kilometers ranging from east to west and about 3 kilometers ranging from north to south. The total length is 13.7 kilometers. It is 12 meters high, 12-14 meters wide across the top and 15-18 meters thick at the bottom. Xi'an Ancient City Wall is used for defense.