What large weapon did Leonardo da Vinci design with a bow spanning about 25 metres?

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

Leonardo developed the design around 1488–1489, probably while seeking employment from Ludovico Sforza in Milan. The weapon was intended mainly to project fear and launch large stones or bolts rather than to function as a practical battlefield arm.

Its great bow was mounted on a wheeled frame, and a winch or mechanical system would have drawn the string. The design used laminated wood and other materials to increase flexibility and strength. It was never built as a working weapon.

The giant crossbow is often confused with Leonardo’s giant catapult designs. Those were separate studies, although both belonged to his broader investigations into military engineering and mechanical advantage.