Medieval walls were large, fortified structures built around towns and castles during the Middle Ages. They served as protection against invasions and attacks, often featuring towers and gates for defense. These walls were typically made of stone or brick and could be several feet thick, making them difficult to breach. In addition to their defensive purpose, medieval walls also defined the boundaries of a settlement. Many towns had a series of walls, including an outer wall and an inner wall, creating layers of security. Some famous examples include the Great Wall of China and the walls of Carcassonne in France.