Leonardo da Vinci designed a giant crossbow with a bow spanning about 25 metres.
The weapon appears in Leonardo’s military-engineering studies from the late 15th century. Its enormous bow was mounted on a wheeled platform, and a mechanical system was intended to draw back the string. Leonardo may have envisioned it as a psychological weapon as much as a practical one, because its size would have made a strong impression on an enemy.
The design was not a simple enlarged handheld crossbow. It included a broad supporting frame and mechanisms for loading and releasing the projectile. The proposed scale also created major problems involving structural strength, stored energy and accuracy.
There is no reliable evidence that Leonardo’s giant crossbow was built or successfully used. It is best described as a design study showing how he applied mechanical analysis to military technology.