Medieval fortifications were structures built to protect towns and castles from attacks. They often included thick stone walls, towers, and gates, designed to withstand sieges and invasions. Common features were moats, which are deep ditches filled with water, and battlements, which provided defenders a place to stand and shoot arrows. These fortifications varied in design depending on the region and time period. Some famous examples include the Tower of London and the Castles of the Loire Valley. Over time, advancements in military technology led to changes in fortification styles, making them more complex and effective against new weapons.