What vehicle did Leonardo da Vinci sketch with an armored, conical cover?

Leonardo da Vinci sketched an armored fighting vehicle with a conical cover.

The design, drawn around 1487, resembles a large covered platform mounted on wheels. Its sloping armor was intended to deflect incoming projectiles, while a group of men inside would turn cranks connected to the wheels. Small cannons were arranged around the vehicle so it could fire in several directions.

Modern writers often call the machine a tank, but that word can create a misleading impression. Leonardo’s vehicle had no engine, tracks, or modern turret. It was a proposed mechanical war machine powered by people inside it, and no evidence shows that it was built in Renaissance Italy.

One famous drawing contains a likely mechanical error: the cranks and wheels appear arranged so that the vehicle could not work as shown. Some historians think this may have been deliberate, either to conceal the design or because Leonardo had not completed the engineering details.