A fort is a fortified building or military stronghold designed to protect against attacks. Historically, forts were built in strategic locations to defend territories and serve as bases for soldiers. They often feature thick walls, towers, and sometimes moats to enhance security. Forts can vary in size and design, ranging from small outposts to large complexes. Many forts, such as Fort Knox in the United States, have become famous for their historical significance or strategic importance. Today, some forts are preserved as historical sites, allowing visitors to learn about military history and architecture.