A ballista is an ancient missile weapon that resembles a large crossbow. It was used primarily in warfare to launch projectiles, such as large bolts or stones, over long distances. The design allowed for greater accuracy and power compared to traditional bows, making it effective for sieging fortifications or targeting enemy troops. The ballista operated using a system of twisted ropes or springs to store energy, which was released when the weapon was fired. It was commonly used by ancient civilizations, including the Romans and Greeks, and played a significant role in military tactics during its time.