What enormous weapon did Leonardo da Vinci design with a bow about 25 metres wide?

Leonardo da Vinci designed a giant crossbow with a bow about 25 metres wide.

The weapon appears in drawings made during Leonardo’s service to Ludovico Sforza in Milan. Its extraordinary size was intended to create a powerful psychological impression as well as a formidable projectile weapon. Leonardo proposed a broad bow mounted on a wheeled frame, with a mechanical system for drawing the string.

The design was not a normal handheld crossbow enlarged without modification. Its scale required wheels, structural supports, and a winding mechanism. The great bow would have been difficult to build and operate, and historians generally treat it as a military proposal rather than a confirmed battlefield weapon.

Leonardo studied artillery, fortifications, and siege equipment in the same period. His giant crossbow is often confused with a catapult or ballista because all three are projectile weapons. Its defining feature is the crossbow-style bow and string, not a swinging arm.