City walls are fortifications built around a city to protect it from invasions and attacks. They were commonly constructed from stone or brick and often featured towers and gates for defense. Many ancient cities, such as Jerusalem and Rome, had impressive walls that served both military and symbolic purposes. Over time, as warfare evolved and cities expanded, the need for city walls diminished. Today, many historic city walls, like those in Carcassonne and Dubrovnik, are preserved as cultural heritage sites, attracting tourists and offering a glimpse into the past.