Leonardo da Vinci sketched a tank-like armored fighting vehicle as a circular, many-sided machine.
His design, usually called Leonardo's fighting vehicle, appears in notes from around 1487 to 1489. It resembles a conical turtle shell and was intended to carry several men and multiple light cannons. Wheels beneath the armored body would have allowed the crew to move the vehicle across a battlefield.
The machine was never built for Renaissance warfare. Some historians have noted that the surviving drawing contains a gearing problem that would make the vehicle move backward if constructed exactly as shown. The error may have been deliberate, or it may simply reflect an unfinished design.
Calling it a tank is convenient but historically imprecise: the modern tank emerged during the First World War. Leonardo's vehicle was an armored, cannon-carrying precursor concept, not a modern tracked tank.