The Ancient City Wall refers to the fortifications built around cities in various cultures to protect against invasions and attacks. These walls were often made of stone or brick and featured towers and gates for defense. Many ancient cities, such as Jerusalem and Xi'an, still have remnants of their walls, showcasing the architectural techniques of their time. These walls served not only as protection but also as a symbol of power and stability for the inhabitants. Over time, some walls became less functional as military technology advanced, leading to their preservation as historical sites and tourist attractions, reflecting the rich history of the cities they encircle.