What massive siege weapon did Leonardo da Vinci design with a bow about 25 meters wide?

Leonardo da Vinci designed a giant crossbow with a bow intended to span about 25 meters.

The weapon appears in Leonardo’s military engineering studies from the late fifteenth century. It was conceived as a psychological and siege weapon, using its enormous scale to launch a large projectile and frighten an opposing army. Leonardo’s drawings show a broad bow mounted on a wheeled support, with a mechanism for drawing the bowstring.

The design was not a practical field weapon in the ordinary sense. Its size created serious problems involving material strength, energy storage, aiming, transport, and reliable release. No authenticated Leonardo giant crossbow is known to have entered service.

It is distinct from a ballista or ordinary crossbow, both of which use a bow-like launching system but are much smaller in typical use. Modern reconstructions help illustrate the mechanism, but they do not turn Leonardo’s surviving drawing into evidence of a deployed weapon.