What weapon did Leonardo da Vinci design as a giant version of a crossbow?

Leonardo da Vinci designed a giant crossbow as a large-scale siege weapon.

The drawing shows an enormous bow mounted on a wheeled platform. Leonardo’s concept used a broad, flexible bow and a mechanical system to draw the string, because a weapon of that size could not be cocked by hand.

The design was probably intended to launch large stones or oversized bolts and to frighten an opponent through its scale. Leonardo emphasized mobility, giving the machine a carriage so it could be moved into position.

The giant crossbow is commonly confused with Leonardo’s other military designs, especially his armoured vehicle and multi-barrelled gun. Unlike those machines, the crossbow relied on stored tension in a bow rather than gunpowder.