What enormous weapon did Leonardo da Vinci design with six wheels and a giant bow?

Leonardo da Vinci designed a giant crossbow mounted on six wheels as a proposed siege weapon.

The drawing, made around 1488–1489, shows an enormous bow supported by a broad wheeled frame. Leonardo included a mechanical system for drawing the bowstring, since a weapon of that scale could not be cocked by ordinary human strength. Its size was intended to make it intimidating as well as powerful.

The design is usually treated as a concept rather than a proven battlefield machine. Surviving evidence does not show that Leonardo’s giant crossbow was constructed or used in combat. It is also distinct from a ballista, an ancient torsion-powered weapon, and from a trebuchet, which launched projectiles with a counterweighted throwing arm.